yeah i agree, 150 bhp is about all you'll see with bolt on mods then you'll need to change the cams and go to T/Bs to see more really.
150ps will see you keeping up with most st170s though.
thats assuming all ghias have quite a short ratio MTX box like my ghia estate does so its pretty quick through the cogs(it does 130 on my gps very close to 6k in 5th)