My neighbor recently bought a 96 cobra. It has 60,000 mi on the original motor. The dealer that he got it from told him that it had 400rwhp. I went over to check it out last night and I noticed that it has a CAI, underdrive pullies, off-road X pipe, and some flowmaster mufflers. Neither of us have any idea what else has been done to this car. We decided to go out and race his car against my 03cobra just to see what it had. Anyways his car backfires every time he shifts from 2nd to 3rd under hard acceleration. Every time and only on that shift. Any ideas on what could be causing this? Thanks