I recently finished installing my hedman hedders along with the matching y pipe. i put in the o2 sensor on the collector of the drivers hedder. im currently running open y until i have the chance to weld in my cat. the "dumb" question is, am i supposed to have backfires? when the car is running, it runs fine. only when i go WOT and let off or when i free rev it somewhat high does it back fire. is this normal?

 

is it BAM, a loud backfire when increasing rpm's or is it pop pop pop as you left off of the gas?

 

Is your car carbureted? If so you have to remember that fuel will still be pulled into the engine when decelerating in gear. When this happens fuel vapor fills the exhaust and if the ratio is right you get a back fire. Usually a series of pops.

 

my car is tpi. and when i let off the throttle it will pop pop and bam

 

It sounds like its just pulling fuel into the engine, blowing it out the exhaust and reigniting when it gets a bit of O2 on the exit. Heres a suggestion, Put a cat back and tail pipe on, maybe. lol This will certainly take care of the potential fireball under your car.