I am NOT a Tech Expert, but for what it's worth, I have had some success in cleaning the MAF on our '98 E320.

I removed the whole unit from the duct , then removed the sensor from the housing (needs special screwdriver or ..) . I blasted the flow through surface first with brake cleaner (I have lot's and it gives a good blast) and then all metal parts with electrical contact cleaner. I then made a wad of paper towel to fit in the flow thru opening, soaked it with contact cleaner had pulled it back & forward a few times. Also cleaned MAF plug contacts and put in a little dielectric grease.

First time I did this, it lasted for 3 months. have just it again and will see if it works this time!

Wonder if the high current cleaning cycle that is supposed to actuate each time the car is shut down may not be working, but don't know how to test it.