My 2 cents:

05 STi

Dead stock with exhaust only = approx. 230hp (Speedworks dyno)

Recently (March 07) still with stock turbo and Verso retune:

Full 3" turbo back exhaust
Apexi panel air filter
1.35bar boost (holds consistently through to redline)
11.6afr with 82% injector duty cycle

= 273hp & 360Nm on ASG's new dyno which reads lower than Speedworks

Very little lag, very few mods, 400-450k's to one tank of fuel and pulls hard to redline - gotta be happy with that!