Gidday, assuming that the problem is not the fuel pump.
It could be that one of your coils is faulty.
I was in a week long tarmac car rally last month here in NZ (www.targa.co.nz
We had a similar symptom in the wee Renault Megane RS225 we were running.
Once the car was hot we would get a miss under heavy load. There were no errors in the daignostics to show this fault. We were away from the main cities so we purchased a single coil from a car wreckers. We swapped the coil out one at a time until we removed the miss. Fixed.
The offending coil was breaking down when it was hot and under load.
Certainly worth a try. if you can get one. Maybe borrow one from another bike to test. I am not sure if the coil is the same for a bunch of bikes. Maybe check max BMW parts fische.