Someone at the track mentioned that a popular fix to this problem on other cars is a to drive a small tube in the vent hole of the PS reservoir cap that empties into a bottle attached in the engine bay.
Anyone has tried that? That sounds like a great solution. I wonder if a simple kit already exists. If not, someone should make one.
2009 E90 M3 | SG | FR | 6Speed | Akrapovic Evo | JRZ RS1 | StopTech Trophy | Cantrell Brake Ducts