hi guys

i was wondering if someone can help me. ive got a 1990 s2 and it doesnt seem to have any go to it, it seems to boost up ok in 1st and 2nd but seems to strugle in 3rd 4th and 5th when up to speed it goes ok until you come on boost again.
compressions are all the same it had new plugs and leads fuel filter etc but still the same.

plz help cheers dave