The airflow meter potentiometer can cause problems with the idle control. You need to get closed loop control also, maybe first. I don't remeber the actual symptom we are working with.
The .88v reading is a rich reading. Its either right or wrong. You should adjust the fuel mixture lean counterclockwise till it runs bad or till the voltage drops on the sensor. Once the voltage drops to .6 or less the control can take over. The EHA current should be around 0-3ma (usually right around 0 but I have seen them creap a bit) with the sensor disconnected. If you hook up that .88v sensor the current should go negative up to 12-13ma trying to lean it out. It will succeed if the mixture is lean enough. But it only has so much capability.
On the airflow potentiometer, I look at the resultant output voltage. This is what the computer sees and is such because the computer is in the circuit. The usual voltage around idle is about 1v (.7 to over 1v could be I don't recall) but the important thing is that it stays constant with reguard to airflow plate position. This can be tested with the engine off and the key on.
Bosch Master, ASE Master, L1
33 years MB technician