MY99 uk impreza turbo.
This is what i have got.
1000 rpm to 4000rpm she pulls like a dream then she holds back.

changed the MAf sensor
changed the air filter
checked the boost controller
changed the fuel filter.
Still got the problem but not so bad

Where are the coil pack's

WHAT DO I DO NEXT?

 

have you checked the plugs like I said on your original post?
Do you have a CEL on the dash (Check Engine Light)?

You wont have coil packs on that model of car, just one coil. If you havent checked the plugs I would do so, possibly clean them up (ideally replace with new) and maybe regap them to .5 (usually its .6 or .7) If it runs better then it could be a weak spark that is being blown out as pressure rises in the cylinder