Sounds like you should've bought an evo since it is pretty built from the factory. However, this is a wrx forum, what kind of turbo's were you looking at for your '07? What are your power goals? The '07 Sti's are showing pretty nice numbers when tuned, since they have a slightly different turbo for this year.

 

Some people have held 500 on STi's some people can't hold 400. It is all in the tune and supporting mods, make sure you don't have a super aggressive tune. If you are looking to go rotated, you should be fine with a 30r on stock block but a 35r would deffinetly be pushing it. A 20g or FPgreen would both be nice, safe, streetable turbo's though.

 

Moving to STi Engine Performance.