are you looking at a fmic down the track? probably better off getting the fmic at the same time as the powerfc to save 2 tunes
with full exhaust, filter, 10 psi boost and some sort of ecu, you should get what you are aiming for easy
edit: oh, and when i up'd the boost to 10psi, i also had missfire which was quite violent on some days (to the point where the car would just miss from the lights) and non-existant on others. Regapped plugs to 0.8 but didnt do much so got new coils which fixed the problem