Bad coil causing hesitation?

[Vaden85SEL]

Hi,
I have an '85 500 SEL. It has always had a somewhat rough idle, and it used to have hesitation upon take off when the engine had come up to temp. After replacing plugs, wires, distributor cap, and all the stuff in a usual tune up, it still hesitated. So I had the vacuum system smoke tested and found that I needed to replace the injector cups and seals. I did, and the car ran great for about 3 months.
Just recently, I drove a 1200 mile cross country drive and it performed great the whole way. But about 2 days after the long drive, the hesitation and rough -er idle has popped up. I cleaned out and tested the actuator on the idle control valve and replaced the hoses connecting it as they were brittle and cracked. It didnt help. So I thought maybe it had to do with the O2 sensor. Replaced it and the car still hesitates. I checked the mixture and found it was a little rich and leaned it out a smidge.
I don't know what to do next! I have read on a few posts that sometimes the coil being bad has been found to be the culprit. Does this make sense? I mean, if the coil were bad, wouldn't it hesitate and idle roughly while warming up as well as when hot? My 500 SEL runs great while warming up, but when it is hot, the hesitation and rough idle come out.

Any help will be very appreciated!