1999 Nissan Primera Lack of power

starts first time every time, runs fine, lacks power and jerks like it hiccuping when you put it under pressure in 4th and 5th gear usually when going up hills on the motorways, i have sat and reved the car to above 3.500 revs it seems to hold back and lacks power. i have changed the fuel filter which made it a little bit better. i hope that you can answer my question
Thankyou
Alan