peterac

hi,
need some help cause i cant find anything specific enough, anyway.
having realy bad power loss in mid rev range, when i try to accelerate hard it judders a bit and slowly accelerates when it gets around 4000rpm it starts picking up quickly and then accelerates properly. my car is a 99 impreza 2.0 non-turbo gl. have a cone airfilter on but was the same before that. plugs are fine and im stuck now. anyone who has had same problem how did you sort it? id love any ideas even daft ones if they have reasoning. thanks alot people.