Here is a link to my previous thread, which gives a run-down of the problem:
Hesitation again ('90 300SE)
Found car was running lean (flucuation around 75%). I watched the DMM as the car warmed up from dead cold. was around 50%, but then started to head upwards (leaning out) as temp gauge hit aprox. 60C. Enrichened the mixture so that it flucuated around 50% while in closed loop operation.
I also discovered that the air intake sensor was not attached. what happens if it is not functional? Anyways, obviously reattached it.
So, car runs like a raped ape now. Idles great too, can't even tell she's running.