I have a 328i and I am wondering if anyone can help me. Every now and then I get the chance to accelerate up to about 100-120mph. This if fine exept that when i slow down, if I brake relatively hard (pedal halfway to end of travel) I notice a certain noise coming from the brakes. If you blow air out of your mouth and let your tongue vibrate to it, it kinda sounds like that. sorry but i dont really know how else to describe the sound. When I look at my rotors after the aforementioned braking, I see bluish streaks on the disks. Usually they are nice and circular which go around the whole disk. They wear away after a few days and braking performance is not lost. Is this bad? Is it normal? Any of you who track your M5's ever have this?