most stories like this turn out to be plugged radiators. you replace the thermostat, flush the radiator, worry about the VFClutch, replace the pressure cap and nothing works. i think that specially in the case of a used car where the PO didn't regularly replace coolant or used non-MB stuff, the deposits will accumulate and eventually clog some tubes. there have been recent cases when two year old radiators were found to be clogged and causing the elevated temperatures. i suspect that mine is not 100% free flowing anymore and have since moved to a "cooler" thermostat which is working for me. i don't believe that the citric acid flushes are enough to dissolve the types of clogging i am referring to. the rads have to be dipped in those special baths and the tubes reamed out. that, or get a new one -i would check out those remanufactured ones that are half the price....
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"