I am suspecting that I have a bad MAS. Has anybody tracked the voltage output versus load? Can I assume that it is fine since I havn't received a CEL?

 

I didn't have to suspect long. Yesterday I received the dreaded P0105 engine code which is "MAF circuit failure" on my 1999 E430. After taking it out (takes about 60 seconds to get it out) I cleaned it out by reversing wind across it backwards as well as generally tapping it to clear off foreign material. A great deal of MAF's generate CEL's just because they have mung on the conductor surfaces. This keeps the MAF rebuilders in the chips since many cores just need to be cleaned and then resold. After clearing the CEL it came back after 10 miles of driving. I found the incredible buy on Ebay under
98 - 10 MERCEDES MASS AIR FLOW SENSOR METER MAF S500 S430 1130940048 0280217810

The price is about $24 including shipping and this part fits almost all 430 and 500 engines plus some 55 engines. These are listed as brand new parts so I will give them a try and keep everybody posted. The website (wholesale mall) in Tampa has them and has sold 176 of them so far with shipping 7 days out. The part numbers on them match my OEM part to the letter. Twenty four bucks? How can you lose on this one!

If I am not satisfied with the above part I will research buying just the element instead of the complete assembly. There are only two screws holding the sending unit on the housing so you don't even have to remove the housing from the air tract but these two screws are security screws of what looks like either T20 or T25 size. The bad news is that they are five point instead of 6 point security screws so they can only be unscrewed with this somewhat rare bit. Some tool shops carry them or ask a local shop to 'rent' the bit for a few hours. Rebuilders like Cardone and others will most likely be able to furnish me with a rebuilt element since I can read the OEM part numbers on it while still installed in the housing.