ECU driving me to drink

I hear what your saying and have done continuety tests on all the earth pinouts to my earth and all tested ok.
I have driven the car with 2 of the ecu's on 300 mile return trips , and with one if i drive under 60mph , it drives all day and night .With the other it will drive all day and night if I dont turn it off . All i do to swap between these in un plug one and slide the other in and plug that in . No other changes. If my wiring or sensors had issues , why would they both run but have completely un related problems ? I have swapped them back and forwards many times and the same faults stay with the same ECU's