Rough Idling

Hi, I'm new on here and to the mercedes scene. I,ve just bought a 1989 300se and would appreciate a bit of advise before i spend hours checking everything.
 
The problem i have is ! The car starts first time and runs sweet as a nut while the choke is on, but as it warms up and the idle drops the tick over gets very irratic and cuts out at full running temperature. Once at full temperature and cuts out you need to use full throttle to get it started again. If you hold it 1500 rpm it still runs and drives great. I should mention that the middle box is blowing and i am changing it this week, I know exhausts can effect idle but never seen it make this much difference.
 
All suggestions would be greatly appreciated
 
Thanks

Those particular model did have some Throttle Valve Actuator problem, you can rebuild those...
 
take care,
-mar-

Thanks for the advice, I had a few hours spare yesterday and went down the back to basics route. The previous owner had serviced the car but on closer inspection hadnt checked the distributer cap or rotar arm. Which where long past thier sell by date. I didnt think it was the main cause of the problem because of how well it ran while it was cold, but i have replaced them tonight and am pleased to say the car now runs perfect