The exhaust wont effect you cat at all. What might cause your cat to go bad is engine misfire and maybe abnormal afrs. What mods do you have on your car?

Here is a nice site to give you some ideas: http://www.villa-automotive.com/ReasonsFor...rterFailure.htm

If your cat is going bad, I would have it checked out. Its not uncommon that I see cats go bad from engine misfire but the one I see a lot of is with cars that are really low. Ive seen a ton of converters get smacked pretty hard on speed bumps, etc. and they start to break the honey comb inside. The problem should be addressed so you arent stranded somewhere when the converter goes completely bad (similar to sticking a bannana in the tailpipe or something. lol). btw, the bannana thing prob doesnt do anything. One hard rev and it will prob shoot that thing right out. haha

 

I just got mine installed at RPI this past monday and i love hearing the exhaust go off when i start the car. Best thing to do is listen to that car take off. Can anyone say BEAST!