[PhantomRider]

I'm doing this upgrade shortly, from everyone I talked to and read, the smaller boosters require more vacuum. Plus most say you should have 15-20 inches of vacuum for any of them to work properly. However there are guys here running them with much lower vacuum, the problem with not enough vacuum though is low rpm driving and stop and go driving, like in traffic when you don't wanna fight yer brakes. Basically without enough vacuum, manual disc brakes would be better, as with little vacuum that is basically what you are doing with the power set up and creating a harder pedal where as the manual disc are set up to acommidate this with how its valved and power is not as it uses the vacuum to achive the proper geometry in the valving.