My Audi 80 quattro with 2.0 L 115 hp ABK engine (149000 km) still causes problems when running the engine. If the accelerator pedal is quickly penetrated in idle mode, the engine first swallows itself before turning up. When driving in the lower speed range (up to 3000 rpm) there is always a jerker when taking the gas and when giving the gas afterwards the car is jerking again. I also have the feeling that the car does not really hang cleanly on the gas up to 3000 or 3500 rpm. The acceleration is very slow in the range. From 3500 rpm the engine is running very well. Only from 5500 onwards it gets tougher again. When reading out the fault memory, of course, no errors occur. I have already changed the cooling water temperaturer, the Lambda probe, the throttle valve mpoti and the air volume meter. Also all vacuum hoses. What else can the problem be caused by? Control unit or knocked out throttle flaps?