On my 85 500 SEL, I had a similar problem, although not to the same extent.. The car would be difficult to start, and idle really badly. When the engine was hot it was even worse. General performance was lacking.
It turned out that my CO adjustment was way too low. Make a note of the position of the screw, and turn it clockwise to increase the mixture, anticlockwise to decrease. If it does nothing, or make the car worse, Turn it back to the original position.

Ben.

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Ben

'85 500 SEL
'85 928S2
'88 560 SEC
'90 750i