I’ve recently had ECU problems with a 75 & I learned the following. New or blanked (Sometimes called virgin) units will need to be programmed to the car if you want the engine immobiliser to work. They can do plug & play versions but I don’t know what that involves. You can have your unit cloned as well or repaired. If using a donor unit, all the part numbers must match & should come from the same model of car as yours but it will still need reprogramming to your car as it’ll be programmed to the original one & will interfere with it running. (I believe it can be done from another model if the programming codes start with the same letters or you have the unit blanked 1st.) Hope that’s helpful. Not an expert though.Does any one know anything about the ECU? From what I've been told to have a replacement it would require reprogramming when replaced or is the ECU before purchasing should be already programmed? The second issue is the Alarm immobilizer which I want to replace, but not sure where it's located. Any advice please, much apricated.