I own a new 2001 E320 (it happens to be a wagon) that has had a strange, intermittent noise coming from the front of the car since the day I got it. This noise occurs only during modest acceleration ..... slow acceleration or hard acceleration makes it go away. I would describe it as a high frequency "rattle" that is coming from in front of the driver. It's probably in the dash or the engine compartment. It might be engine knock (I'm using Moil premium fuel), but it doesn't sound like any engine knock I've heard before in other cars. Sometimes it occurs when the engine is cold and sometimes when it's hot. On some days, it doesn't happen at all. The dealer is mystified. Help!!