Quote Originally Posted by green91
Gees people there are some bad answers in here.

#1) A brake booster will NOT EVER cause a soft pedal. A bad booster will make the pedal HARDER.

#2) Are you sure they are bled correctly?

#3) Check for sticking slide pins on the calipers.

#4) Ive seen many new master cylinders that are bad.
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.