Alright....so let me just say that I'm not really that knowledgable when it comes to exhaust stuff. I am currently in the process of swapping out my tired old TBI L03 (in my 91 RS) to a carbed 350.

When looking at exhaust systems, do I get the model that is the same as what my car came with stock? My basic question is....do they just give those specifications so you can select the system that physically fits the underbody of the car best? So if I get a cat-back for a 91 VIN code E car, will everything be okay?

Second.....when it comes to replacing cats (since mine needs to go, and I want to have a cat), I wouldn't need one with an AIR tube, would I?

Thanks in advance!

 

With a cat-back you would indeed go with the version for your model car. Headers are a different issue. You will not need A.I.R complient cat's unless you plan on using your smog pump and all that crap (if you are why bother swapping motors) remember to plug your exhaust manifolds if you don't use the A.I.R

 

yep yep. For headers if you get anything that is for a 91 VIN code E then it most likely will be for a 305 and the header size will probably smaller than you would like, 1 5/8" when you most likely want 1 3/4" since you have more displacement.

 

1 5/8" primaries will be fine for a 350 up to 400hp. 1 3/4" will make a little more power up top, but you will have great low end and really strong high end with the smaller of the two. Now go over 6500 rpm and make more than 400hp and you will need 1 3/4".

 

I'm going to beg to differ here. Getting any exhaust intended for an LO3 when going to a 350 is borderline criminal.

Get everything for '86-'90 TPI single cat application. This will give you 3" at the cat, 3" cat, & 3" cat-back.

LO3 stuff is tiny - 2-1/4". Dump it all, and don't buy anything like it for replacement.

 

We all agree on that. We were talking about header primary size and already assumed the rest of the exhaust was 3".

 

When getting headers get something intended for a single cat l98 car. Like hooker 2055's. They will have a 3'' collector on the Y-pipe.

Then get a catback exhaust for a l98 single cat car like a hooker catback.

Then do away with the cat...of course