good luck!
youll want to check every line that comes leads away from the the intake after the MAF sensor, some of it depicted here on realoem:
https://www.realoem.com/bmw/enUS/sho...diagId=11_6122 youll also want to check the hose going to the brake booster and the booster itself. if you dont find anything blatantly obvious (the ecu can compensate for minor leaks) you might want to go back to checking basic stuff like fuel delivery, spark, etc.
I'd also refrain from spraying rubber parts with brake clean. It'll dry the rubber out and cause more issues down the road.