First of all, thank you for replying. The vehicle already has a brake booster as well as a vacuum reservoir, so I just need to add a vacuum pump & pressue switch, right? no need to get another brake booster, the thing is how to know what size vacuum pump I need regarding how much vacuum does it pump, which is CFM as I understand. Thank you,The easiest way is to use a salvage, or aftermarket new, OEM brake booster vacuum pump - no science needed there. Some also have pressure switches.