Right now, my 1997 Z28 is throwing me a Service Engine Soon light. I had this checked w/ an OBDII scanner, and it turns out that one of my cats is not functioning properly, and that's why it's throwing the light. That's not really a surprise, a few months back I had a misfiring problem and drove the car while misfiring (not for all that long, but apparently for too long)

So I have to get smog tested in January, and I'm wondering what I should do. I'd think a high-flow cat would be better than an OEM cat, but would it still work fine and prevent the computer from throwing codes?

I was also looking at the Random Tech High-Flow Y-Pipe, which seems like it'd be nice, again as long as I can run that with the stock O2 sensors and not throw codes.

I'd like to come out of this spending as little as possible, and if I get a bit more performance as a result then that's fine. Are any cats besides OEM legal for use in CA? I'm reasonably sure I'll get reamed on price if I buy an OEM cat, so that's why I'm thinking aftermarket is a good plan.

Also, is there any way to tell which of my cats is messed up? Should I just replace both?

Thanks in advance...

 

Oh, and is there much chance of me causing any worse damage by driving around with a messed up cat?