I've heard about this before, - but I may be missing the point.

The thing is the original EEC-IV ECUs program/map is hard wired in the factory and cannot be changed without a chip. It is not possible for the program to spontaneously change on it's own.

That being the case if your car "started" doing this on its own one day then it can't be a fault with the ECU program. Something else must have gone wrong which is causing the problem.

You may be able to cure the "symptoms" by tweaking the program to ignore whatever is causing the problem, but are you addressing the root cause?

My EFi CVH works perfectly well on the original map, as does the spare ECU. What is the code of the ECU that's in your car?