Matt01GT

There is a popping sound coming from my exhaust. The car idles very rough. I was told that it was normal for an 01-03 GT for that to do that because of a sensor in the transmission from the mechanic. I believe that to be bull****. I also changed the spark plugs to see if it was a misfire because when i am in 5th gear the car bucks when i am driving on the highway and a lot when i open the throttle. If you think you know what the problem is please let me know. I also have an SLP loudmouth catback and a mac offroad midpipe. I higlhy doubt that the popping sound is because of mixture of exhausts but i though i would throw that out there too.

Chopper

Sounds like this are impossible to diagnose without being there to hear them.
See if there are any codes stored in the memory and repost.

22kart22

sounds like backfiring if you know what that is.. is it running correctly