if i used a 2.5" dp for my turbo application would i need to replace all the piping in the rest of my exhaust system to 2.5"? 94 LS

 

what exhaust are you running now ?

if you are running stock, I would strongly suggest getting a 3''.
if you are running a 2.25'', you will be OK, but still a 3'' would be ideal

 

I went from a 2.5" Tanabe Racing Medallion to a custom 3" exhaust with a 3" Apex N-1 on my 99 turbo SI and it was a world of difference. No boosheet! With a 3" exhaust I was running the same 1/4 times when I used to run no exhaust.