My car (85 190E 2.3) has a similar problem - hesitates a lot when cold. All secondary ignition parts have been changed. Today I got the O2 sensor replaced. The tech said it should fix it. Lets see - I am not that optimistic any more. Did you get the airflow sensor checked? My own reading leads me there - it sure is an elusive problem. Let me know what fixes it for you!

Rags