General Motors Corp. Chevy HHR SS TURBO W/ OHB Braking System 2008 HHR SS Turbo Brake failure due to Optimized Hydraulic Brake system Detroit Michigan

Bought a 2008 HHR SS turbo and found that the brake system fails to work after the car sits for over 8 hours or more. Ive contacted GM and have dealt with the dealer to get this issue fixed but was informed that the brakes are preforming ok.
The dealer tells me that the brake booster fails to receive vacuum from the engine for the first 2 or three minutes of operation after the car has sat for a extended period of time. This makes the pedal rock hard and feels like the ABS is trying to take over but the car doesnt stop. GM has used this same system on the Pontiac Solstice turbo and the Saturn Sky turbo and have the same service bulletins on these cars.
2009 HHR SS panels will also use the OHB system and will have the same issue. Ive had my vehicle in the shop three times and still its not fixed. If the brakes fail to work would GM be responsible seems that they insist that the car is safe to drive?

Jason
fremont, Nebraska
U.S.A.