Check your option list according to VIN for the option S322A Comfort access. When it is activated you have to notice if your car opens doors keyless. See the Product Information, page 36:
https://www.google.ru/url?sa=t&rct=j...87269000,d.bGQ For the F10 LCI models, the keyless tailgate operation comes together with the keyless door opening.
If nothing is present, go ahead with the M5 diffuser. Otherwise the tailgate sensor can be relocated.