I had spongey brakes and had replaced booster. rotors and all brake pads. I tested brakes and heard a click and felt a slight click in pedal, this only happened once when pumping the brakes after replacing new parts. I bought new master brake cylinder and tested brakes again. brake pedal stiff and brakes do not release until i bled one brake caliper and or unplugged the vacuum hose on booster, then the brakes released. went back and forth trying to find any issues, bled the ABS valve, still stiff brakes with no release. The remedy/FIX ... I compared the center pin with the old booster pin, ( on the booster that plunges into the master cylinder ) and the new booster pin was 1/16th an inch longer. I swapped out new pin with the old one. brakes work great as they should. Hope this helps someone else with this kind of issue, PEACE