Mike, my hesitation problem only occurs when the temperature outside is below 40 degrees F. The car starts and runs fine, but as it begins to warm up it hesitates very badly when accelerating from a stop, like 0-60 in five minutes, which can be dangerous. When the car reaches normal operating temp it runs fine again. I'ts been doing this for three years now and I have not found the problem.
The car is an '88 260e which does not have an air intake temp sensor. They must have started using them in '89 or '90. My wife's '92 300e has one. For the air/fuel mixture adjustment I used a multimeter to measure MA through the EHA and adjusted to get approx. -2 MA. The reading before adjustment was -8 MA (too rich). All adjustments were made with the car warmed up and running closed-loop, (O2 sensor connected).
The EHA on my car had a very slight fuel leak, more like weepage that was noticable when it was hot out. I replaced the o-ring seals which seems to have cured it but I have also heard that a leaking EHA means it is no good. I am keeping an eye on it to see if it leaks at all and maybe needs to be replaced. I might try swapping it with my wifes car since the part numbers appear to be the same and see if that helps the hesitation.