So what is your EHA current? is it the same with the O2 sensor disconnected?
The airflow pot only has a small capability to affect EHA current. A quick voltage change from low (less than 1v) to high (above 3v) will cause the acceleration enrichment function to act. This adds at most 5-10ma.
The main defect I see with the airflow pot is the lack of proper idle speed control.
Bosch Master, ASE Master, L1
33 years MB technician