Whak me in the head for being stupid ... I guess MB engineers those cars like no other. Humbly ... I stand corrected ... clearly I exceeded my knowledge ... have to love all this technology (adaptation???) ... can't imagine how I coped with my dumb old 1964 Chevy Nova and a carburator, points, etc.

One thing for sure ... the "adaptations" are not going to get reset anytime soon ... I live in Dogpatch ... no one around here would have such a sophisticated scanner except the MB dealership in Mayberry ... and I had one experience with those guys already ... not sure I want to clean my non-smoking ashtray out again and clean up after someone's lunch And not to mention paying $800 for a 30 minute job. I guess my grandiose plan for getting that smart CEL light to go out in a reasonable time is shot to heck in a hand-basket.

Oh well ... the car is almost 11 years old ... and I'm going to drive into the ground anyway. I'll just return the MAF and the pressure regulator ... save myself nearly $350.00 and an hours worth of work in the heat. As soon as I finish typing this I'm out to the garage ... I'm going to pull out the instrument panel and pull the little expensive bulb that lights that great CEL light ... the car runs great ... until it starts to run poorly ... the CEL light can take a hike.

Like i said, it will relearn/reset as you drive it.. Just will take some time to reset itself.

I am happy to report that the $127 MAF sensor insert from germanstar.net has cured my P0170 CEL problem. To my pleasant surprise, in addition to the elimination of the annoying CEL, the car now has MORE POWER, it shifts smoother, and up-shifts quicker than with the old sensor. With the original sensor 0-60 mph took about 12-14 seconds. Now it is 8-9 seconds!. (This with transmission in regular "drive" mode", both cases). After resetting the old sensor (battery disconnect) the CEL would re-appear within a day or two. I have been CEL-less for over a week with the new insert. Too soon to determine effect on gas mileage.

I bought the car (1997 E320 sedan, 70k miles) used in 2004, and the CEL appeared soon after the purchase. For a variety of reasons (expensive MAF, not certain the MAF was the cause, car ran "good-enough", the CEL tripped only when coming to a stop after driving at freeway speed - a transitory problem, good mileage 20-24 mpg) I resisted buying the complete MAF unit. Even $270 for the MAF assembly seemed a poor bet, not knowing for sure that the MAF was the true culprit. I scoured this and other forums looking for knowledge and cheap fixes. Searching for vacuum leaks, cleaning the sensor with MAF cleaner, blocking the charcoal canister (virtual vacuum leak), new air filter, plugs, wires, etc. Nothing worked. (But thanks to the posters for the advice nonetheless -- educational!)

It was just a few weeks ago that I discovered (I think in this forum) the availability of the MAF insert from germanstar.net. $127 was a relatively attractive bet. It has paid off in spades! Here's a big THANK-YOU to the poster steering me to germanstar, and to all others posting on this topic