I have non-catted Pacesetter LT's and the TSP Dual exhaust. Ever since I had the long tubes installed, I have been getting MAJOR backfire. I had my plugs changed to TR55's except there was one that all bent, so they took the best looking plug and put that in it's place. I haven't had time to have the codes shut off yet, but I know the engine runs a bit rich without the cats, and egr, etc. Do you think the plugs could be gapped incorrectly, the old plug is misfiring, my running rich, or that is just the exhaust and that's what happens?

It backfires when I drive through towns. I'll be sitting at a red light, gas it up to 3k and back off as I slow down at the next light/stop sign and it literally sounds like a cannon is under my car after a few quick pops.

 

tuned?

 

Nah, not yet. Another factor I have put into question.

 

I think a tune is in order here. In my experience, whenever one of these cars has next to no backpressure it will pop like that and a tune usually will fix it. .02