I have been bothered with this problem for some time now and have recently done more checking in an effort to understand it more -- all very interesting but to no avail so far. I am experiencing very long cranking time and long rough start up idle (couple minutes depending on temp) which isnt the normal smooth 560SEL motor.

Steve B's link on the Bosch system was a godsend and I have checked only the mixture control off pin 3 of the X11 connector which seems to behave normally --
-at open loop (key on engine off) very rich setting.
-once started the duty cycle moves around about 10percent indicating closed loop operation and I am able to adjust the mixture using the mixture control tower screw for the air flap.
-the mixture was a bit rich if anyting and I adjusted it to a more lean condition.

Does anyone know whether these settings affect start in a cold condition???

Many thanks.