I have a 1988 Audi model 80 Quattro which suddenly began giving symptoms of misfiring or stuttering under acceleration. Once the engine rpm increases (about 3000 rpm) it runs smooth until I grab the next gear where the misfire/stuttering starts again. Once up to speed and at a constant speed it runs fine but any change in throttle setting will exhibit the symptom again until the rpm increases to around 3000. So far I have changed plugs, wires, fuel filter. I have also been running seafoam/injector cleaner through the last few tanks of gas. I also checked to make sure the upper coolant temperature sensor is changing with the temperature(about 5.6Kohms at 65degF). I didn’t change the O2 sensor but I think this is a more severe problem than that sensor could correct. I also removed the CIS rubber boot to make certain the large butterfly was able to move freely. It seems that the idle speed control works, at least the idle becomes erratic when I unplug it. I was wondering if the fuel pump is putting out sufficient pressure but it seems to work fine at higher rpms.???