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Chevrolet Impala Accessories & Modifications



  • atbearatbear Posts: 322
    A VIN for a 2003 LS Sport is: 2G1WH55K639115280

    As you can see, I've already been through all this =)
  • atbearatbear Posts: 322
    I just heard that the DHP PCM is available for the Impala now! I'll have more info when I get it! This is great!
  • Really that is great news! Yea keep us updated. Thanks.
  • Hey
    I went down to the dealer and got a VIN off of an LS Sport, and now I am getting cluster number 10306212. The vin I used was 2G1WH52K639151040
    and I got the clusternumber from gmpartsdirect. So now I'm really confused between the part numbers. Guess I will just order from someone who will take it back if it is not the right one.
  • garnesgarnes Posts: 950
    We have a 98 Aurora - 4.0 V8 and a 2001 Impala LS. The Impala is the wife's car and she doesn't want anything modified, but I have made some changes to the Aurora and dyno'd some of them. I'll share the results just to give some idea.

    I realize that the 4.0 DOHC is a very different motor, but the results are interesting. In light of some the conversation, it might help. The Aurora is 250 HP, 260 torque stock.

    All my dyno results are at the WHEELS. All dyno's were done the same day - back to back. The Aurora drivetrain loses about 24% whereas I've seen the Impala drivetrain estimated at only a 21% loss. You can see the dyno's on

    I gutted the air box and installed the K&N panel. The K&N panel filter added 6.5 to 7 HP to the peak - not much below the mid 4000's. The air box mod allows more of the filter area to be used and it added 2.5 ot 3 to the peak torque, but no peak HP. It also add 1 to 3 HP from the mid 4000's and below. With both together there WAS a noticeable difference - especially punching it from a roll. Whether you "feel" it or not seems not to be so much a matter of how much peak power it adds, but a function of how much power it adds through the power curve. I wish I could modify the Impala air box, but is does not seem to be as workable. It only uses a small area of the filter and I believe a K&N would greatly help the car - my guess - at least 5 HP at the engine. I do have the K&N panel in the Impala though.

    I had a bored out throttle body added. It went form 75mm to 80 mm. This added 5.4 peak HP, but did a great job adding power all over the curve. Fattened it up more than 5.5 in a lot of places. I definitely felt it. Later I bored the mounting plate (or plenum) to 80mm as well so everything was matched ported to the manifold. That probably added another 2 or so.

    I put a cat back exhaust from Corsa. It was made for the STS but works great on Auroras. Anyway, the exhaust is the best improvement you can make. My system is all straight-through. No baffling. It like having a straight pipe (but quiet because of some cool sound cancellation technique). Corsa dyno'd an STS and it added peak 21 HP at the wheels. Granted, this was a 300 HP engine that revs very high (breaths hard) and is probably bottled up pretty good with the factory exhaust. I'd expect some good gains from a similar system on an Impala. My guess would be 7 or 8 HP - 10 at the engine.

    I know "Thrasher Charged" made a decent looking intake for the Monte and it probably fit the Impala.

    Good luck.
  • garnesgarnes Posts: 950
    Maybe this has been posted before. If so - sorry.

    RSM does some good stuff. However, I'm not to keen on the idea of the open cone filter drawing hot air off the engine. I think the thrasher charged intake (an enclosed cone) is better.
  • atbearatbear Posts: 322
    Looks like your did some good stuff to your Aurora, garnes, but it really doesn't apply to the Impala too much.
    What I mean is, adding just a K&N panel filter will give no gains whatsoever by itself. Gutting the airbox and then adding a K&N Panel is ok, but really the only way to go would be a K&N Cone filter. You're just not getting enough air through that airbox.
    The exhaust on the Impala flows fine. No gains (maybe 5 HP being generous) will be felt at all with a cat back system. It does sound good though (I have the Borla).
    There is a great Throttle Body out for the Impala. Go to to see it.
    I've done a TON of research on modding the Impala, and I think I'll have mine around 270HP when I'm "through"... should be next month sometime. I'll post my mod list, plus what I'll be getting next month. Thanks for posting, and Good Luck to you too!

    2002 Impala LS
    FWI w/ 9" cone, Borla Exhaust, MandS 3" DP/Cat/Ubend, 180thermo, BMR Swaybars Front and Rear
    ZZP High Velocity Upper Intake Manifold
    ZZP Stage 2 High Velocity Throttle Body
    LS1 Fuel Injectors
    ZZP Extended Range High Ratio Rocker Arms
    DHP PCM Tuned to ZZP Stage 2 Specs
    INTENSE Pushrods
  • atbearatbear Posts: 322
    Also, guys, please don't waste your money on RSM Racing!! There are much better and cheaper places!!!
  • 02lssport02lssport Posts: 75
    Damn bear your car is going to rock.
  • garnesgarnes Posts: 950
    atbear - you've really done a lot. Wow. Have you ever looked into the thrasher charged guys in Indiana? Any good?

    Yes, the Aurora is quite different, but some of my experience may shed some light on how much mods help.

    Hey - I dyno'd that K&N panel filter with the stock air box and it added some nice power (all tests back to back - same day). They do work. I even dyno'd it on more than one occasion when I was there to test other ideas. It's too bad that people dismiss them so often without any proof or testing. I think their claim of 2 to 4% gain is pretty good.

    The Aurora air box isn't the greatest., but is very different than the Impala. When you "gut" it, you really get a nice flow through it. There is a big opening under the box that can be exposed for more fresh air from behind the fender. Another Aurora buddy did the cone filter set up on his car and dyno'd it and the results were about the same as my panel - really. The key is that filter media is SO much better than paper- that's the big difference.

    Just MHO here - I'd be concerned about pulling hot air off the engine with an exposed cone filter. Hot air will lose you power.

    How do you know the Borla doesn't add much power?? Any dyno's? Have you gone to the dyno for any of your other mods?

    RSM can be expensive - but hey , for me, who else is doing Northstar stuff and Aurora V8 stuff??

    If you have dyno'd your Impala or taken it to the track or anything, I'd like to know how you did. Maybe the wife will let me "touch" the LS. Also, how do you like the Borla??? How is it at cruise on the highway??? Is it straight through, or does it use some baffling??? Packing???? Overall, how polite is that Borla system???

    How much $$ is that throttle body??? My understanding is that the TB and MAF are together as one unit on the Impala.
  • atbearatbear Posts: 322
    "Have you ever looked into the thrasher charged guys in Indiana? Any good?"

    Yeah, they are good guys... They're cage car is really fast. They are more race oriented than street performance oriented though, so I wouldn't go for their cam unless you don't plan to drive your car everyday! It's very aggressive!

    "The Aurora air box isn't the greatest., but is very different than the Impala"

    Right, you won't see those kind of gains by the K&N panel on the Impala, the stock airbox is too restrictive. If you gutted the Impala airbox you might see gains though! I don't doubt the gains on the Aurora V8.

    "I'd be concerned about pulling hot air off the engine with an exposed cone filter. Hot air will lose you power."

    You ARE certainly right there! The is very true. That is why I have a Fenderwell Intake (filter is in the fenderwell). I get cold air all the time! I had a Thrasher Cold Air Intake box, but I found it's quality to be less than perfect, so I sold it, and did the FWI.

    "How do you know the Borla doesn't add much power??"

    I haven't made it to the dyno yet, but others have and it really doesn't do much unless you open up the exhaust before it as well. The stock catback on the Impala isn't the restriction, it's the downpipe and ubend on our cars that is the restriction starting point. I got my exhaust because I've done downpipe/cat/ubend too, and I like the sound!

    I went to the track stock and ran a 15.9 in 99 degree temps (I live in Baton Rouge, LA). I was running the same as a late 90's Mustang GT! Now I'm probably a few tenths faster, but not a whole whole lot. Once I get all my other mods I'll probably be low 14s in the 1/4. My ultimate goal is 13.999.

    I love my Borla. It's NOT loud at all (people with Grand Prixs who have it sometimes complain it's not loud enough). But, it does have an awesome low tone. There's not a lot of drone with it either. And the quality is TOP NOTCH. Borla is straigh through design- best flowing on the market! I believe it's 2.5" into 2 2.25" pipes. Dual dual tips. It'll last forever. It's kinda pricey though. And if you have anything other than an '00 Impala, you'll have to get the 2nd hanger welded on, cause they changed that in '01 and Borla didn't update. I personally would suggest the GMPP Stainless Exhaust for a cheaper solution. They didn't have that out when I got my Borla. It's getting good reviews.

    "How much $$ is that throttle body??? My understanding is that the TB and MAF are together as one unit on the Impala."

    Yes, the TB and MAF are in the same unit, and are controlled together. That's why the TB is so important, makes great gains, and is a good mod even for a lesser modded Impala. The link to it is here: m . That is the Stage 1, and the Stage 2 will be out soon (I'm getting Stage 2).

    Let me know if you have anymore questions... I've been researching this a long time, so I like to think I'm pretty knowledgable.. for a TON of info on our cars though, go hang out on . That's where I've learned all my stuff. Good luck!
  • garnesgarnes Posts: 950
    Thanks. You certainly have done your homework. The cone in the fenderwell sounds great. That info about the exhaust is really interesting too. I guess if the exhaust before the converter is lacking - then yeah, the stock exhaust is probably pretty good for what gets to it. I'll print your post out if I ever get an opportunity to work on our 01 LS. Very interesting about the Thrasher charged intake too. That thing looked good, but maybe that cone is a bit too stuffed in there. It may experience a lot of bad turbulence around the cone.

    One thought - a simple K&N panel on the Impala may actually help more than you think. The way I see it is that because the box only allows a small area of the filter to be used, it's got to really hurt airflow. Therefore, opening it up with the K&N media may seem like a huge relief for the engine - unless the used area is so small that it is still restricted even with the better media. Another way to look at it is this - if the air was evenly drawn through -say - 2 sq.ft of filter (just for illustration here - that would be huge), paper would probably not offer much more resistance to flow than the K&N. As the filter area used gets smaller, the paper hits it limit as to what it can flow and resistance to flow probably goes up exponentially whereas the K&N panel may still be flowing OK without some exponential loss yet. Just a thought.

    Back to questions - where/how did you improve the downpipe and U bend? Is there a kit?

    You know, I do get ticked off at GM sometimes. That 3.8 is a great performer - I love it. But it seems GM will strangle these engines with half baked intake and exhausts. Why? For instance, the reason (my theory here) why the air box is so restrictive - it's to keep it quiet. If the box had more volume inside and used the entire filter area it would probably resonate more. The Aurora box used some double wall stuff - but on the inside so it was only slightly better flowing. If they want to keep things quite - double wall it on the outside.

    The exhaust - no excuse for that. Throttle body too. A bigger TB is better for everything - even economy unless you hammer it too much.

    Anyway, I just have to add that my other car is an overhead 4 cam 32 valve V8 (with one heck of a record at Indy) and I still have a lot of respect for the pushrod 3.8 in our Impala. I get tired of the pushrod bashers. They are great engines they offer economy, affordability and good performance.
  • 02lssport02lssport Posts: 75
    You can buy the downpipe, cat, and ubend replacement as a single bolt on. There is one at that looks like the best option.
  • 02lssport02lssport Posts: 75
    I have read that many GPers have had the u-bend and resonator removed by a muffler shop as an inexpensive way of opening up the bottleneck and having a sportier exaust note.

    Any thoughts???
  • garnesgarnes Posts: 950
    That TB looks great. That is pretty reasonable when sending back the core too.

    What will be different on Stage 2???

    The description makes it sound as though they taper the transition from the TB. That would be very good.

    Also, when I dyno'd my TB on the Aurora (bored from 75mm to 80mm) it did indeed add power all over the curve. So I don't doubt the claims on the link saying it adds power throughout the curve. I really noticed it. Better throttle response and all.

    I tried to tell RSM that the TB would be better if they tapered the transition from the MAF to the TB (on Aurora) and make it more bell shaped. They never listened. That one you link to seems to incorporate this idea.

    Is it hard to do?? How do you get the TB off on the Impala? I can't even figure out how to get the rubber boot off the unit.
  • atbearatbear Posts: 322
    I have read that many GPers have had the u-bend and resonator removed by a muffler shop as an inexpensive way of opening up the bottleneck and having a sportier exaust note.
    Any thoughts???"

    The ubend is a restriction, the resonator is not. Depending on your planned mods, the best route changes... for a quick fix just do the ubend. For a complete fix get the DP/Cat/Ubend and a Cat-Back system.
  • atbearatbear Posts: 322
    "What will be different on Stage 2 TB???"

    Stage 2 should be way better. I believe the only mod on the Stage one is porting, but the Stage 2 will have optimized MAF tables and such.. and might come with larger fuel injectors.

    "Is it hard to do?? How do you get the TB off on the Impala? I can't even figure out how to get the rubber boot off the unit."

    It's super duper easy. You just pull the boot off with force. And then the TB is held down with four simple screws. Very easy and quick.. Yes the new TB is tapered for High Velocity!
  • garnesgarnes Posts: 950
    Thanks. That sounds easier than the Aurora. I'm always afraid to use a lot of force on anything. I take it that you have to mess with those throttle cables too - but those aren't that bad I guess.

    I'm tempted to do this. Sounds cool.

    Can you give me some idea of what is better about the after market drop pipe? Difference in diameters, smoother bends, stuff like that. What's so bad about the stock one? That is interesting.

    Also, any links to your intake would be cool - or did you fab that yourself? Yours sounds very good.

    If you did the drop pipe, and Borla, would you get some good gains?
  • atbearatbear Posts: 322
    I don't think you have to mess with anything... but probably just unhook/rehook them. I've never done it before.

    The Downpipe is pretty small. It's 2.5" pipe, but it's insulated, so the I.D. is even smaller than that! I got a 3" DP/Cat/Ubend all the way through with a 2.5" exit to bolt onto my Borla Catback. With the DP/Cat/Ubend and Catback, you'll probably get about 10-15HP total, and that's if you have already done intake. The exhaust really isn't restrictive in it's stock form. But once you start modding, it becomes restrictive.

    I had a Thrasher Cold Air Intake Box, but it wasn't working like I'd hoped (when you stopped at a light or in taffic, the heat would "leak" into the box). So I sold it and made a Fenderwell Intake. It's pretty good (better). Give me your email and I'll email you my directions. Another option for you is to wait for the ZZP Intake that'll be coming out. It's should be the best thing out when it's released. It's like the Thrasher, but better sealed and with more available air. The Thrasher was pretty low quality. Let me know if you have any questions...
  • garnesgarnes Posts: 950
    atbear - send me any info at Thanks. Pictures are cool. I may do some of this someday. The TB is really interesting.
  • I'm working on a custom grill for my '03 Impala. Does anybody have the part number for this piece, or even better, access to a drawing? I'd like to use the original drawing to be sure I've got the dimensions correct.

  • atbearatbear Posts: 322
    The Impala Grille is Part # 10289769 and it's $107.80 from the factory.
  • ghostwolfghostwolf Posts: 91
    atbear, I spent some time at the dealer and I got a second opinion telling me the number was 10306212. Then I spoke to mechanic who said sure everything was fine, we had to order the cluster and then they would send it off somewhere else to be programmed.

    Then I got home and got a call from the parts person who told me that GM said that you can't switch them out, it would not work. So I'm not going to take no for an answer, I'm going to go back and talk to the mechanic again and then try to get it set up to where at least if it dosen't work out, I can get money back on the cluster.

    I will keep you informed and let you know if/when I get it done.
  • atbearatbear Posts: 322
    Hmm.. everything you said makes sense, except the part number I have for LS SPORT is 10306213. I know I'm right, unless it's been changed in the past 2 months. I'm not saying you aren't right, but just make sure before you order. Good luck, let us know what happens!
  • txguytxguy Posts: 57
    I saw the earlier post about going to a Xenon lamp. Does that really improve the output? These LS stock fog lamps seem to be for appearance only. They are pathetic in the fog as I have found out each morning this past week during my 55 miles daily trip to work. We've had thick fog each day.
  • 02lssport02lssport Posts: 75
    I'm putting xenon's in place of the factory fog lights real soon so I'll let you know!
  • jeffreyw1jeffreyw1 Posts: 145
    Does anyone know if there are any good vinyl floormats, that cover most/all of the carpet area in the front floorboard, being made? Also, does who manufacturers/sells these have any that are close to the neutral color of the 2001 Impala? I would like to find some because I have some of the cheaper floormats which do not cover very much space. Thanks for any and all input!
  • tommy42tommy42 Posts: 70
    try Mats For Less
  • 2002ls2002ls Posts: 11
    I ahve a 2002 LS and I have upgraded to 130 watt xenon bulbs. They throw out a bit more light, but the real problem is in the reflector behind the bulb. It is very poor compared to other factory fog lights out there. I am going to try and put a mirror coating on the reflectors, I'll let you know if it works.
This discussion has been closed.