Correct me if I'm wrong, but a bad air/fuel ratio can burn out your cat right? If so, then what causes a bad air/fuel ratio? does it have something to do with your CAI?

Bad O2 sensor

Any number of problems can cause your fueling to go bad, O2 as Cheetah mentioned is the most prominent killer of cats.

ok, so what would be the main causes for your fuel to run rich? The reason I'm asking is because I'm replacing my exhaust next week due to cat failure and I'm just trying to figure out why so I won't run into another cat failure.

possibly a vaccumm leak too .....i just fixed my car running rich and that'* waht it was..a simple vaccumm leak



James

I do have a rubber fitting on my fuel rail that is dry and a little cracked? And I know I need to change that o2 sensor.