I've read over the posts again. Have you checked the coolant temperature sensor?
The AFM pot will only influence the ECU same as the temp sensor. I think it might be time to check for continuity from the ECU to the EHA. ECU to AFM. Coolant Temp sensor to ECU. Also measure the resistance at the pins of the ECU plug per the manual for each sensor.
You should not have a rough idle with the EHA disconnected, in fact if anything in a good condition engine the idle could be even smoother (at running temp) as there is no closed loop control and no (very) minor fluctuation in idle as you see with rich/lean correction. This of course is only if Lamda is set correctly mechanically.
Besides cold hard start, I imagine cold rough idling. You must make the measurements at 80 deg C with respect to duty cycle. Are you seeing a fixed number now or is it fluctuating? How about general driving, is it still stalling? Car will stall if the mixture is badly adjusted or the Zero position/Basic position of the AFM throttle plate is incorrectly set. Have you checked that?
87 190 E
89 190 Sport Evolution