[GTHAUS]

FYI, our TYR TECH (stage I) tune is not detectable by BMW service center (Dealer).
With Down pipe upgrade, it is obvious that you "MUST" have some sort of coding upgrade, not to have the CEL issues,

but we know that dealer (service bay) equipment will not be able to detect such software upgrade unless as someone mentioned above,
BMW factory engineer with advanced factory equipments (more capable) starting to analyze your car.
At least that's what we know so far.

Most of all, it ultimately really comes down to the dealer(service)
and also who you know and who you are dealing with at your dealership...