You can't really go too big for an exhaust on a turbo car. It's not like a NA car that needs a little back-pressure to prevent valve-float. The headers, up-pipe, and turbo provide plenty of back-pressure. Turbo drag cars run huge open downpipes that exit behind the front wheel.
Just be prepared to deal with cops for the decibles. I'd check your local law, then call APS and ask how loud it will be. If it won't be too loud, get it inspected after you install it. The DMV should give you paperwork saying it's been inspected. That way, if you get pulled, just show the cop your papers and he'll prob leave you alone.
'06 WRX STi
Last edited by Ian; 09-04-2006 at 08:08 PM.