JPMD

I have no idea if this is similar just chiming in. My previous M5 (F-10) had "charcoal" filters in addition to the STD air filters. Not sure this was worldwide at the time but told as far as US it was to meet California emissions so all US cars had them, When dynoed (other reported cars not mine) they robbed about 10+hp. I had them removed when DINAN piggyback tune was added. Car was obviously faster and felt faster after the tune which added significant power so in reality unable to differentiate what if any difference would have been felt with just removal of the filters alone. The turbo sound was more pronounced for better or worse depending on individual