EN:

I've been approaching your problem from the standpoint of mechanical control of the position of the throttle plate.
In rereading your original post, it seems that you may be describing a change of mixture (or possibly timing).
The primary control of mixture in the KE-jetronic system, as with all K-jets, is mechanical, via the airflow sensor plate and the control plunger. Secondary control in KE is via the O2 sensor, the ECU, and the electro-hydraulic actuator (EHA). The current to the EHA is also modified by air temp, barometric pressure, water temp, vehicle speed, rate of throttle opening, and more, but those adjustments are small and gradual.
It is possible that the feedback signal from the O2 sensor to the EHA is causing a large enough change in mixture to be felt as surging.


INSIDIOUS:

The reference to US models is in my first post, and was to distinguish them from ROTW cars that might have been equipped w/ARS. ARS actuator linkage differs from USA cruise control linkage.