Rough Idle Frustration

[dynalow]

Just took my 1988 300CE in for 45,000 (yes) mi service at an MB dealer. Told rep it had a rough idle.....occasional miss.

Later: "Well..these old steel injectors get pitted and there is bad atomizaton.. you need new ones...brass, better atomizaton,life, etc.

But with new plugs,main fuel filter, and new ingition rotor and cap, "it's still not right." So, we took out your fuel regulator (?) and replaced it with one out of a 91/92 190 and guess what, it's running ok. We'll let you have the car for the weekend, but you need a replacement and the price of a rebuilt is 777.00. Call me next week.

So I get it home and it idles rougher now than before when stopped with engine in gear( with engine temp about 80c and air temp about 70f) and also has a split second hesitation when moving off from a cold start.
The symptoms are a quick irregular misses felt right up through the seat. In gear at idle, the engine is turning about 6000-6200 rpm.
So, I'm down 1,300 bucks and heading further south.

Anyone have any thoughts on where else to look (electrics maybe?) I'm afraid they are just replacing parts hoping to find the problem.

Appreciate the feedback...

Jim