Have you tried a can of good fuel injector cleaner? Have they checked the O2 sensor? Have they checked to see if the Fuel Mixture is correct at idle?

I have a 1986 that had a rough idle. New wires and plugs and cap and rotor, fuel filter, O2, blah blah blah were all tried. Fixed it with a new AFM boot and replacing every rubber vacuum connector. Still was a hair off so I got the Heavy Duty Bosch Copper plugs. Ran great but still not as smooth as I thought it should be so I got a can of BG44K fuel system cleaner. She now is almost as smooth as my 2003. Still has some bumps once and again but I am thinking that is my cracked exhaust manifold letting in outside air or letting out too much exhaust and thus making my O2 get false readings and my EHA to over correct. But check or have checked the following.

Rubber Intake Boot between AFM and Throttle Body
Vacuum rubber connectors all throughout the engine bay
Check Mixture
Check O2
Verify Copper Bosch Plugs used and Gapped correctly
Clean IACV and AFM and intake area with Liberal Amounts of Carb Cleaner
Check Water Temp Sensor for proper functionality
Verify OVP relay is functioning properly

If needed I have a spare OVP I can send you for a small fee that works perfectly. I also have a spare IACV, but mine is a 3 wire deal with the adjuster knob on it and you most likely have the 2 wire one with no adjustment.

__________________
~Jamie
_________________
2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....