Hello I have the Audi 80 B3 2.0e with the 3A engine I have the problem that he if I pull him really well and from exactly 3000 rpm he stops pulling and he has no more power in lower tours! if I turn him off and start again because he is back until I come back to 3000 because that’s again! have already changed air filters and spark plugs! have heard that the fuel filter could be the real thing or what is on the control unit?