Quote Originally Posted by Krytdrgn
Depends on what is wrong w/ the booster. In my old truck, mine caused a vacuum issue causing soft pedal. I replaced the master cylinder first b/c it was already wearing out and then we looked and there were no leaks so it had to be the brake booster which fixed it.
For a vacuum booster to somehow make a pedal softer, you would have to increase the amount of vacuum going to it. A vacuum leak, hole in diaphragm etc would make your brake pedal harder due to lack of vacuum assist. I cannot think of a way that a bad booster would make your pedal softer.