AFTER DRIVING FOR ANY AMOUNT OF TIME AT A HIGHWAY SPEED, THE BRAKE PEDAL IS EXTREMELY HARD TO PUSH AND THE VEHICLE WILL CONTINUE TO ROLL FOR SEVERAL FEET AT SLOW SPEEDS, USUALLY UNDER 10 MPH. FOR EXAMPLE, WHEN COMING TO A STOP LIGHT OR TRYING TO PARK IN A PARKING LOT. VERY UNSAFE. I BACKED INTO A CONCRETE WALL, LUCKILY DID NOT DAMAGE MY TRUCK. AFTER RESEARCH, MANY PEOPLE HAVE STATED IT IS A DEFECTIVE VACUUM PUMP. POOR PERFORMANCE BY GM, NOT TO MENTION THE LACK OF CUSTOMER SERVICE OR BACKING OF THE BAD PARTS THEY ARE PUTTING IN VEHICLES. BRAKES NOT WORKING IN A VEHICLE DUE TO A FAULTY PART IS UNSAFE. I'M HAVJNG TROUBLE HAVING GM EVEN ADMITTING IT'S A PROBLEM, AND I HOPE I DON'T INJURE OR KILL MYSELF OR SOMEBODY ELSE BECAUSE OF THIS ISSUE. 71000 MILES