Hi again everyone, so I have a spare highline BECM, but my car has a lowline BECM and was thinking of just swapping the logic board from lowline to the highline unit but have read on forums it won't work necessarily so I wanted to ask around if anybody had any luck with doing that. Both are taken from manual diesel P38, the highline is from a DSE 1996 and the lowline is from DT 1997.

It would need all the security stuff copying into the Highline. There are places that can do the cloning. Also unless they relicate the mileage (kilometerage ?) then the Instruments or BECM will update to whichever is higher.

If you have the correct FOB(s) & EKA for the Highline, it would probably work, but the milaeage issue still exists. After you write down the new VIN, EKA, etc. you could disable EKA & Immobiliser just in case.