420SEL Stalling. Help with the diagnosis!

[Panzermann]

So, my 1991 420SEL with 202,000 on it. Problem is that occasionally, seemingly at low speed, the engine will shuts off. It happened this AM. Just stops.

Recent stuff that's been done
1) EZL Ignition control module failed about 3,000 mi ago (the engine just stopped while car being driven), replaced with used one.
2) New rotor, distributor cap, spark plug wires 10K ago.
3) New spark plugs, 1,000 mi ago
4) New Fuel distributor 500 mi ago. Engine was running rough at idle. Number 1 and 3 cylinders were not firing. Back to baseline after replacement.
5) Fuel injector seals and air feed tubes replaced.
6) Fuel injectors tested and good (after 200K!)
7) Fuel filter replaced

Machanic told me that idle speed not being as well regulated as it should be, and I sometimes observe it running a little high (900-1100 on the dash tach). suggested this could be a problem with the idel control module or idel control valve (which has a little electric motor in it and would surprise me to still be running normally).

Thoughts????