I just got my car state inspected and the car happened to be asking for the biannual fluid change standard BMW service interval change/flush. Had the dealer go ahead and do their procedure and the pedal is markedly better. Granted I haven't bled the brakes in forever but it was nice to feel an improvement...or terrible that I was so lazy before now
I wonder if having them run the flush procedure at the dealer might eliminate a variable if you haven't done that already? EDIT: Nevermind you did that already
Also, I thought the ITBs (and the lousy vacuum you get because ITB's) meant vacuum assist comes from an electric pump on our cars? Maybe that is failing or not able to keep up with demand, or there's a leak developing when hot?
http://www.realoem.com/bmw/enUS/show...diagId=34_1627 #8
Not sure if that could cause your symptom but it's a system you haven't thrown parts at yet,
Unfortunately I think if you're using MDM the most likely culprit is going to be the ABS system, MDM uses the ABS pump quite a bit to get the job done, and you may just be a victim of an outlier premature failure, but hey who knows maybe it's something really dumb and cheap you just haven't checked yet
EDIT again: I think if it was vacuum related the pressure sensor would trip a code? Realoem diagram has a vacuum pressure sensor in-line to the booster