C124 cutting out

[FMalan]

The car's engine cuts out sometimes;
Most of the time it occurs once the engine is warm and always at low revs/ idling speed. Typically when you slow down (no foot on accelerator or brakes) when taking a highway exit and just coasting to a stop. As the revs go lower it just cuts out suddenly. It immediately starts again though.
It is not as if the engine is starved of fuel - its a sudden cut out as switched off.
Car is a 1240502B076917 1990 300CE (South Africa) and to date the local MB agents have ruled out the following;
distributor cap and rotor
air slide
fuel pump relay
ECU
voltage protection relay
ignitor box

Any advise is appreciated.

Thanks
FM