Have a 2014 CM S All4, ~81k miles. Recently had a complete loss of brake boost, and the half power light on the tach came on. Definite reduced power and was not easy to slow down as the brake pedal was rock hard (identical to when the engine isn't running). Visually checked the car for leaks or anything like that, nothing that you could see or hear. Carefully drove the car home, I noticed that there was no turbo whistle or sound of the wastegate that I normally hear during a typical drive, and the half engine power light stayed illuminated.

After visually inspecting the lines for the brake booster, I pulled the vacuum line from the vacuum pump, and felt no vacuum whatsoever. I also went ahead and hooked up a vacuum pump and no vacuum registered on the gauge.

I'd rather not take it in to the dealer, and I'm wondering if anyone else has experienced anything similar? I see threads with a sinking brake pedal, but not much with both loss of brake boost and apparent loss of the turbo.

Any ideas before I jump into replacing the vacuum pump?