this has been discussed a bit (mostly by myself to myself :-) ) but possibly I can get others interested in this as well. the 'problem' supposedly is a decrease in idle from nominal to 500 or so when switching into gear. Typically everyone mentions the OVP and ICV etc. I've checked these on mine and all is fine - I finally had a chance to speak with a MB service guru who advises these components are seldom (if ever) the problem. In fact a idle of 500 or in gear is perfectly normal! Otherwise the car would constantly creep when stopping etc. so, for all those experiencing a somewhat decreasing idle when under load... do not fret. The idle control valve does not 'neccessarily' keep idle at 'no load' rpm, but, moreover, is there to stablize the idle at a certain RPM and 500 appears to be perfectly acceptable. Definitely the car's rpm will go up a 100 or 200 when not under load. Anyones opinion differ, I'd like to hear.
cheers, guenter