my car has now 100,000km on it.
The o2-sensor was renewed this year and I use an improved emission control electronic together with the standard Bosch KE3 Jetronic to get a better emission rank in Germany, which saves me tax.
I think that the closed mixture control loop makes the rough idle more poor, because when I disconnect the EHA connector the idle gets smooth.
The rough idle got really poor in my car after I cleaned some carbonizing out of the throttle valve which makes the throttle sticking in the idle position.
In my guess there will be some cylinders running lean for any reason and some others try to compensate this by running rich. The average of all cylinders, which is measured and controlled by the o2-sensor, is o.k. (Lambda = 1).
Mil, did you check your fuel system pressure?