• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

Cat Converter question


SM 2007
Full Member
Apr 10, 2007
Grand Rapids, MI
I have read a whooooooooooooooooooolllleeeeeeee bunch of threads and haven't really seen this question addressed. I kind of have a unique situation. I am from CA and that is where I bought my 04 Z71 5.3. CA has strict emissions laws and doesn't leave much room from messing around as far as exhaust or any performance upgrades for that matter.

I now live in MI where they have no emissions laws of any kind.

So the question is do I need to change my converters (CA Truck) or are they the same regardless of the state it was meant to be sold in? I'm pretty sure I need some kind of converters for the back pressure????

I want to do headers and a cat back conversion but I'm not sure if I should just go for the whole header back (headers, cat, exhaust).

Any help would be greatly appreciated  :help:

Without convertor computer will think something is wrong and run for crap....

unless you do some magic...
I dont haver FI so it probably doesnt matter if they stay or go but I would like it to flow nicely so I could get a bit more power/ throttle response and maybe pick up a few MPG........ any thoughts on my current cats ?
FLowing better ?

Stock exhaust flows well and anhy improvement is not neccessarily by allowing more flow as you will lose low end torque...

Check some existing threads froim Muffman...

also from some posting appears max gain possible is 10 hp.... but most notice no difference
I have read alot of muffmans stuff I just wasnt sure if I had some different cats or something do to the fact I bought my truck in Cali........... I think I am going to call GM today and maybe send muffman a PM......... thanks for the input  :wave:
Cats are Cats... no difference fromCA trucks and the rest...

GM cats are high flow...