I was wondering what piping would be best to go from header back. Currently I have a vibrant cat back system that is 2 3/8 piping.

I was planning on getting a high flow cat and then having an exhaust shop in town fab up some header back piping so I have a larger exhaust from header back.

My question is what high flow cat would be best to use with the 2 3/8 piping of the current cat back? I was thinking either the 2 1/4 cat or the 2 1/2 cat?

Now depending on which cat I should get would depend on the exhaust piping size. If i were to get the 2.25 cat I'd get 2.25 piping the whole way through up to the cat back system, if I were to get the 2.5 cat I'd get 2.5 piping the entire way to the cat back.

I always had the idea that an exhaust system should go from small and then get bigger so that leads me to believe I should get 2.25 piping and 2.25 cat? What do you all think? I do want to keep the current cat back I have now seeing that its not even a year old.

Just so you know i'm trying to free up air flow so I can build up a minor N/A motor; bolt ons, some internals, an underdriven crank, and a good tune.

Nobody gonna help out?


Motor Mounts - Trans Mount
4-1 Header - Catback Exhaust
62mm TB - B&M Shiftplus

id go with the 2.25 cat and piping you don't want to go big then choke it down

Thats what I thought. Thanks for the answer.

I know this may be a dumb question but, I live in pennsylvania so would an obd2 complaint magnaflow cat still allow me to pass inspection? I was planning on getting this cat; https://www.turbotechracing.com/productcart/pc/viewPrd.asp?idcategory=510&idproduct=2708

Thanks for any help!


-- Motor Mounts & Trans Mount --
-- 4-1 Header & Catback Exhaust --
-- 62mm TB & B&M Shiftplus --

yes....you will still pass no matter what cat you have, as long as its a certified cat (ie: magnaflow)



soon to be supercharged, eibach sportlines, KYB AGX struts, 18" RTX poisons