The topic starter is talking about a Weber ECU Rod, not an aftermarket one.
And yes, his Weber ECU may well be 30 years old... as was the one in your car.
They suffer immensely from RFi and have virtually non existant internal noise filtering.

Put an unshielded loom in a Cossie engine bay and pop a decent scope on it and watch what happens to the voltage output when you move the king lead near the sensor in the engine bay.
Better still, emulate it and you can watch it change load sites yourself. The loom needs quality shielding and needs the grounds installing in the correct place.

Even better - Try the same test with some of the old Magnecor leads on and you wont even have to move the HT leads as the blody engine will go so rich it missfires sometimes. LOL

Also, while the P8 has the best filtering of all the Weber ECU's of that ERA, Ford still produced a sub loom for the map sensor back in 1993 with even better shielding as they had problems of the car not starting under cranking due to the interference from the starter motor.

We are talking about cars from the 80s here that still had interference suppressors fitted to coils and alternators so that you could listen to a radio or watch a TV in a house on the same street as the car was driving.