I have a car that had an issue with rattling wastegate(BMW 335i) and I saw that there was a retro/update/fix to the wastegate. Everything went great but the customer came back with the check engine light.

The DTC was 2A18, heating of the DTML system. After some digging the car does not have this feature since its made for the EU market. And there is no undo on the wastegate "fix" in the retro programming.
Any other way I can reverse the software update??

Best wishes, Henrik(Im using a Maxisys908s)