http://www.rockauto.com/catalog/x,ca...,parttype,5132 4cyl
http://www.rockauto.com/catalog/x,ca...,parttype,5132 v6
I believe that truck probably uses OBDII .. you can usually read trouble codes yourself by shorting a couple of pins in a connector under the dash ... also most chain stores like autozone will read your codes for free
Figure out how to reset them and then have two different people read them for you (or read them yourself)
If you don't have emissions testing, have some asshole weld pipe in place of the cat. The right person will do that if you give them the cat since they have platinum and other shit in them. Otherwise if you want to stay legal, they have "high flow" cats on ebay for $50 ... they're basically garbage and the same thing as having it straight piped