PhilW: When changing ecu would you need to pair the new ecu with the car even when new ecu has the same part number (identical to the one youre swapping, just a different tuning map) and is a direct replacement???

Prebs
 
When changing ecu would you need to pair the new ecu with the car even when new ecu has the same part number (identical to the one youre swapping, just a different tuning map) and is a direct replacement???

Prebs

Yes you do. You are pairing the immobiliser. Nothing to do with part numbers.