I'm in the midst of an air mass sensor experiment. The check engine light came on on my 94 E320 - the idle would fluctuate from normal up to about 1200 rpms, pulled a code 10 from the DM plug and a code 4 from PIN #8. Disconnecting the plug resulted in exagerated symptoms. Putting in a known to be good sensor eliminated the problem immediately. So in short - the air mass sensor clearly had failed. I tried cleaning it - with electrical contact cleaner - put it back in the car, same problems. Then took it to a jewelry store and had it ultrasonically cleaned (something discussed in another post here) - put it back in the car, car has now worked fine for a week. It operates just as it does with the good sensor in the car. So to me the conclusion is pretty clear - an air mass sensor can fail just because it gets dirty, and ultrasonic cleaning can bring it back. What I don't know at this point is how long it will now last - a few more weeks or a few more years. But ultrasonic cleaning would seem to be at least an emergency measure, to get you back on the road - and perhaps more than that. I don't really know anything about an E430 - whether it's the same technology or not. If it's similar, installation should be a few minutes, not a few hours.