Wish I hadn't read your post just before going to bed. Been lying awake for hours!
You asked for any thoughts, so here are a couple.
Overheating: The only thing that comes to mind that would cause intermittant overheating is an intermittantly functioning thermostat. If it were mine, I would install a new one and await further developments.
Missing: I would be very suspicious of injector problems. Two possible courses of action (if it were mine). (1) Dismantle, clean and check each injector in accordance with MB manual or (2) obtain a rebuilt injector, install it in number 1 cylinder, check operation. If no improvement, install injector removed from number 1 cylinder in number 2 cylinder, check operation, etc. This wouldn't take a lot of time and when you got through you would know for sure if it is an injector problem.
As is so often said on this site, "Just my $.02 worth." Best of luck!
[This message has been edited by Ted2222 (edited 07-30-2000).]