Ive already searched, I want to upgrade the downpipe to 2.5in by making my own, for my greddy turbo(TD05-18G) on a b-series. Im sure this has been done already just need some info from that person, What exhaust flange can be used on the turbo housing?or should I just bore out the exhaust outlet on the stock greddy piece and replaced the old 2in down pipe with a 2.5 one?

 

look at www.atpturbo.com, thats where i got my flange for my greddy turbo

 

That is a T25 internally gated downpipe flange. Check w/ ATP turbo, as there are 2 "5 bolt" flange styles.

 

sorry to kinda thread jack, but if the original poster/anyone else reading this thread has a Greddy kit/turbo, if you have upgraded to a new higher pressure actuator and still have the original 5.5psi actuator available in G.W.O please pm me i desperately want to buy.