I didn't think the zex kit caused the cat to fail, I thought maybe the nitrous has the engine out of tune. I'm not questioning your setup, I know your the nitrous guru around here.

If your going to order from Kteller.com be very specific on the specs for the carsound converter. I've ordered from them in the past and actually got a carsound that was to short and had the incorrect flanges. Not to take anything away from Mike because I think he's a good guy.

There's another "Mike" over at http://www.ipsracing.com that does a very good job. Just to throw another option out there. It's probably more than you want to spend though.