Does anyone know how restrictive the factory cats are? Does anyone make better flowing cats that can be put in a custom exhaust system?
If I go with the long tube headers, do I have to feed the cats to the dogs? haha, or do I just have to get rid of the pre-cats? I still need to pass smog sniffer.

 

Personally I don't think the stockers are that restrictive.

You lose the pre-cats if you install long tubes.

But you don't need the pre-cats to pass the sniffer.
IMHO you need to make sure your cats remain hot when you get tested, don't let your truck cool-down.

I have Magnaflow high-flow main cats, gutted pre-cats (so it looks like they are there - we have a visual check here too), and I passed the CA smog sniffer no problem.

 

Based on the information on the dynatech performance exhaust website our stock Cats have a max flow of 257.1 CFM - the ones they sell have an advertized 396.4 CFM. I have a set of these on my truck with long tubes and so far so good - Then again I don't have the inspection worries others do so can't talk to that.

Dynatech Performance High Flow CATS

 

i ran several types of cats including the random tech ones on a chevy that i owned. i ended up with the carsound cats from magnaflow in the end after a mishap tore up my random techs. they flow well and are cheap in price and most exhaust shops that carry magnaflow have them in stock.