I warmed up the car good with a short drive to the store, got i back home. I am going to declare victory on the rough idle. I did one last fine tune of the on-off ratio. It still oscillates just a small bit, but the value is in the exact same range as at 2500 rpms. I can also trim it out anywhere by turning the screw, it is neat to see the control system adjust the ratio to compensate for the richer or leaner mixture. So now I know it is doing what it is supposed to.

Many causes for a rough idle. I replaced:
1) O2 sensor (just because)
2) Warm-up compensator (failed cold pressure test, not by a little bit either, it was clearly off), new one was right in the middle of the acceptable band for temp I took the reading at.
3) Replaced the lambda control unit. The old one was malfunctioning with a wide swing hunting for a value.
4) Added the shunt line around the ICV, I don't think this was necessary and I noticed no difference in idle.

Interestingly, the car seems a touch more sluggish now. I guess without that rich charge getting blasted into the engine with no compensation, it is just not as peppy.

Summary VICTORY over the rough idle.