so the other day, i swapped out my header, and i had to run a damn open header, so after driving like 5 miles my check engine light came on, but i did not worry about it because i was running the open header, so the next day i got my hi-flow cat on and my skunk 2 cat-back on, and i was driving down the road and it came back on..... and i don't know why, then today i was looking at how much gas my car was sucking up. what the hell can it be?? can me 02 be going bad? i really need the help...

 

uhh check the code????????? that might help.

 

that and what kind of car, engine, OBD? are you running?