i have tpi 305 in my 86 Z. the exhaust is completly off of it with the exception of the manifolds. My question is that i have 2 differant exhausts to use, and need your advice on which one to choose. I have the stock exhuast/y-pipe (dual cats) that came on it and i have a dynomax 2.5 inch (i was told it was dynomax, not postive though) cat-back with a high-flow converter and the y-pipe, all which came from an 84 Z HO. which one would you suggest i use? does the 4-bolt flange set-up from the 84 hurt or help flow? Does it flow better or worse than the later years models? Any help is greatly appreciated.

 

There were no stock dual cats in '86.

 

well now im completly confused, i bought an 86 Z with dual cats, thought all along it was stock exhaust, but still, which one do you think would flow better?

 

well if someone put a factory dual cat exhaust on your car, then i would have to say that is the better one..

my 1991 formula came with factory dual cats with the 3 inch i-pipe.. adding a few more horsepower over past factory exhaust..

i think you should do some measurements and see what you have.. measure the i-pipe, measurement the dual cat inlet/outlets..