GM Genuine Parts Power Brake Booster Vacuum Pumps are designed, engineered, and tested to rigorous standards, and are backed by General Motors. The pump uses engine vacuum and atmospheric pressure to increase hydraulic pressure in the master cylinder to provide power assist. GM Genuine Parts are the true OE parts installed during the production of or validated by General Motors for GM vehicles. Some GM Genuine Parts may have formerly appeared as ACDelco GM Original Equipment (OE).