Search button is your friend here mate.

There is plenty of good examples here of stock MY06 STI's with mild mods like an aftermarket catback system and a mild flash tune (verso or ecutek) getting some very nice gains in torque, hp and acceleration. This is well worth doing as it will improve the stock tune and drive by wire lag that comes with it, fuel economy can actually improve and your will get some subaru dak dak rumble.

__________________
Funny looking German Subaru