Ive recently put on a cat-back skunk 2 exhuast on my 94 gsr. I hollowed out the cat to see if it would help any. Now sometimes my check engine light will go on and im lossing gas milage. Someone told me its because the car runs in default mod when the check engine light is on and that the car will run rich becuase of it, and thats why im lossing gas milage. Has anyone ever done this or have any adive besides getting a hi flow cat??

 

i have it done on my prelude and i have no problems.

your O2 might be bad, did you check the code??

 

The CEL may or may not be related to the cat.

The first thing you need to do is check the CEL code and see what it says is wrong.

This will tell you how to check the code: http://www.c-speedracing.com/faq/06.php