Well I have a 91 gta trans am with a basically stock motor. I've only done t-56, shorty headers, cut the cats out, tune up, and an air filter cone. But ever since I cut out the cats its been spiting out small backfires until recently it blew out my muffler and now it'll backfire really loud whenever I leave her in gear and let it whine down. It'll do it between 2500rpms-1800rpms and I was wondering if I can do something to stop it before I waste my money on taking it to a shop to have them fix it. So please if you can any info on how to fix it would be greatly appreciated.

 

Is the oxygen sensor active? If you invoke Field Service Mode, does the CEL indicate lean or rich?

 

Nope. But hey thanks for trying to help me but since I wasn't getting any help from these boards I went to a tech and he told me that My car wasn't running rich it's just that I have an oxygen leak and it sucks air in when I leave it in gear and let it whine down and the air is mixing with the gas to creation another explosion inside my exhaust. So I ordered a Y-pipe to fix the prob. but thank you anyway.