"Are you saying the the MAF sensor was the 'cause' on the 600SEL? So replacing it, fixed the problem? "
That is what I am saying. The problem was that given the conditions the computer was running out of ability to compensate. The MB fix (I might have forgot to say that the dealer had diagnosed the problem to require two new controllers - about $3400) is too give the controller a much larger ability to correct. You can quote me if you like. I am guessing on some of this. I am not sure how wide the window is now. I think it is as large as I said.
Also since I haven't improved on the cars abilities, it is still suseptable to any other seemingly minor mixture glitch. I am sure that the air mass meter had degraded, but it probably would have been acceptable for a long time with the more capable controller software. When I first decided to try and solve the mixture problem I wanted badly to change the fuel pressure. I am sure I could have fixed the car by reducing the fuel pressure by 5psi across the board. There are people making adjustable pressure regulators for use on cars with OBDII software and added Turbos or superchargers. I am keeping a new eye out for such a device.
Bosch Master, ASE Master, L1
33 years MB technician