I see from your 2007 posts you've been there.
On my 91 m103-
Tested the ovp and everything tests perfectly (several times).
With connector removed, 9 ohms between pins.
Engine on (40c temp) 8.8v between pins, dropping gradually as engine temp warms to 6.5v after a minute or two (just a tic above 40c) when I stopped.
Unplug and idle drops immediately.
Plug back in, no change until I restart the car, then idle ok.
Twice have had someone start the car cold (58f outside).
Starts up but will die unless I slightly hold the air flow sensor plate open, then idles cold fine.
This is driving me bonkers!
Any diagnosis help appreciated!