On the LT1/LS1 Camaros/Firebirds the aftermarket 'downpipes' or headers were often 1 7/8" (x2) and downsized into a 3" pipe. By what is being said here, all of their exhausts should have been 3.5" , but that was not the case. Do you lose that much going from a 3" downpipe with cat and into a 2.5" cat-back? It makes sense what is being said here, but when I reflect on my previous LT1 Camaro and the power that was making with a 3" single cat-back it makes me wonder.

Thanks for all of the information so far everyone! I'm still trying to figure out this car, but love it so far! I am now leaning towards the Magnaflow cat-back even though the cost is higher. I have plenty of cash wrapped up into my Vette which is why I'm trying to slow down a bit on this new sport wagon.

Brian

 

n/a cars you want some back pressure. turbo cars you don't want back pressure at all.

 

get a catless dp and call it a day. if you have emissions or need to go to the dealer for work, swap the stocker back on. really no point in changing the muffler unless you are looking for a different sound cause it won't do anything on the performance side....stock exhaust isn't that restrictive. the hp gained isn't worth the expense imo.

 

Are you on crack?!?!?! a catless DP picks up around 15WHP after a tune... thres 2 cats on teh stock one and a flat part between them. Turbos like to breathe.. the less restriction the better...

 

b i n g o!!!

 

Get a catless downpipe and keep the stock catback