To determine if you are running rich you should get it scanned with a tactrix cable. Your A/F learnings will show with learningview.exe , if they are maxing at 15+ or - then you have a problem with your air/fueling system. My guess is that there is an excessive vacumm leak that is maxing out your A/F compensation at 15, and making you run rich. This could explain the destroyed cat.
So find some one with a Tactrix cable and a laptop already with Learning view and Rom Raider.
Local sub forums may come in handy. Offer beer for service.