if the tubes are clogged from deposits no amount of flushing will clear them. you need a chemical dip and i don't even know if that can be done on these rads that have plastic parts. if you go through the posts, some will say that your temps are normal. i would guess that you have partial clogging in your radiator. my car behaved the same way and i now am running a lower rated thermostat (83C) that keeps it closer to 80C than 90C. my theory is that there is a thermal equilibrium point (the range that 800 for mercedes mentions) that will tend to move up higher with less cooling efficiency from the radiator caused by clogging. once you go over that zone the system will not be able to dump the excess heat without the help of the aux fans. stop and go driving makes it go beyond that zone, for instance. up to a point, this will be ok but eventually you will reach a danger zone where you will continually reach those elevated temps and be in danger of overheating. the approach i took makes the system take longer to go past that equilibrium point and if it ever does, it cools down fast. my other option is to replace the radiator which costs about ten times as much as the thermostat so i think i can live with the way i have it running now...
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"