Right now I have the 305 tpi and the stock 2.25 single cat setup. I have an electronic cutout right before the cat. Since I need a new motor I am getting a 350 and keeping tpi. I'm not sure if I should keep my setup or go to the dual cat setup. Pretty much, what I'd like to know is will a stock dual cat setup and 3 inch catback make more power that my stock 2.25 inch with the cutout open. And if it does, is it enough to justify getting it.

 

You will make more power with the dual cats and an aftermarket cat back compared to your stock set up. Its just now you have 2 cats to worry about and Im not sure on how that all works out with emissions and testing.. but I guess they cant fail you for putting on ANOTHER cat.... can they?

 

yes, they can

 

son of a....

 

Definately go single cat 3" straight back. Just as effective and cheaper overall than the dual cat setup.

 

2-1/4" is TBI size. TPI single cat is 3", dual is 2-1/4" each.

Something isn't adding up here.

 

I think the auto peanut cammed tpi cars may have gotten the 2 1/4 exhaust as well, but I'm not 100% sure on that. Someone feel free to correct me on this.

 

91-92 auto LB9's (205hp) had small outlet manifolds and single 2 1/4 inch exhaust, the 230 hp version had 2 1/4 inch outlet manifolds, duel cats and 2 3/4 inch exhaust. All 91-92 LB9 cars got the L98 cam.

 

Learn something every day.

So, the "real" '91-'92 exhaust is dual cats. Everybody else got stiffed, it sounds like.

2-1/4" with cut-out would be more restrictive than full 3" system.