Question:

I have a MY04 with a Prodrive axle back. I have been looking for a downpipe with a high flow cat. Searched internet, and like the Cobb dp. I called Cobb, and asked if the Prodrive would bolt up to their dp. The answer was sort of a yes, with a but. The Cobb dp is 3", the Prodrive is 2.5". So there was some concern over the last stage of the exhaust going down to 2.5" and causing some restriction.

So regardless of what downpipe I go with, Turboxs, Helix, etc.......

Is there anyone out there running a similar set up, or do I really need to change the axle back to 3" too? Would there be that much of HP loss due the axle back?

 

You'd need a restrictor plate and you'd be robbing yourself of plenty of hp. I'd suggest selling the Prodrive and getting a 3" axleback or a full TBE.

 

With the stock turbo, I'm sure you're not losing significant horsepower with a 3"->2.5" turboback instead of a full 3". Remember as air cools it gets smaller. And that the STi has a 2.5" exhaust.

 

get the bosel down pipe you'll still have the 3rd cat goodluck

 

Try PM'ing fry rice. He has a full exhaust set-up that ends with a Prodrive axleback IIRC.

 

Just get the turbo xs stealthback exhaust. It comes witha down pipe and a mid pipe that tapers down from 4in. to 2.5in to bolt right up to the prodrive muffler. I have that setup and it looks and sounds great. I have been told that you loose maybe 5whp with this setup as aposed to a 3in. exhaust. I would only worry about hp loss with this setup it if you had 300whp or more. It all depends on what your future plans are?

 

A turboed vehicle needs no backpressure whatsoever. It will get all it needs from the turbo.