well guys, i did headers/exhaust march 10th, and at first, no problems.
Several weeks later (probably 2 weeks ago now), my car developed a backfire at 2500. Now, it does not always do it, mainly when going up hills, or trying to slowly accelerate.

Now, what i am thinking
Fouled o2 sensor (but im not throwing any codes)

i ran techron fuel injector cleaner about that time, so could it have unclogged something in my fuel pump, and caused it to clog my fuel filter making this happen?

im out of ideas, and since i have no job, im really low on $$ so i can't just randomly replace things

 

is it possible that since i deleted my cats, theres not enough backpressure causing it to "pop"?