I have a 2005 Envoy 4.2 I6. About 2 years ago we had the ECM replaced with our extended warranty because it was throwing codes. Just recently it started to throw codes. I hooked the computer up to it, and it is reading P0305-cylinder 5 misfire. I replaced all the spark plugs with Bosch Platinum 4's and cleared the codes. The same day, it threw the same code. So I got a new coil and replaced the one in cylinder 5. Again, cleared the code and came back. Took the new coil and moved it to a different cylinder to see if it was the coil and still getting the same code. I have tested the battery, which is sitting within normal range. Hooked a ground wire from the ECU to a different ground to make sure that there was an adequate ground and got nothing. I have looked at the graph on the computer while the car is running and all injectors are pushing the same amount of fuel through them. I am at a loss of what to do. Can anyone help steer me in the right direction?