I have hesitation too
My '88 260 also has a hesitation problem going on three years that I have not solved yet. I replaced the airflow sensor pot which corrected a stalling problem but it still hesitates. I also tried removing the R16 resistor which didn't help. The car would sometimes ping with the resistor out so I put it back.
The hesitation problem I have is only during cold weather - below 40 degrees F. The cars starts and runs fine when cold but as it warms up and the temp gauge hits about 60 degrees C. the car will not accelerate and pressing on the gas makes it go slower. It does this until it reaches normal operation temp. then it runs fine again. I found that the car warms up faster if I don't use the heater so I usually freeze myself just to help the hesitaton problem.
I think that the problem is fuel related and has something to do with lambda or fuel pressure. I adjusted the EHA current to spec's. but I'm wondering what or where to monitor during engine warm-up to pinpoint this problem. I have checked the coolant temperature sensor and it is fine. I have a '93 300e 2.6 that I have swapped some parts with, like OVP relay, also to no avail. I could swap the EHA but I'm afraid it might reqire some re-tuning and then I might have two things wrong which make the problem exponentially harder to solve.
Does anyone have any ideas?