My 1956 Pontiac has a Bendix Treadle-Vac. power brake system. I had it rebuilt in 1984 and it worked fine until this spring. It didn't have much pedal and was low on fluid. I added fluid, but it didn't help. I ordered a rebuild kit and had a local shop rebuild it. The car stops good, but it takes more pressure on the pedal than in the past. Any thoughts on what might have changed and what to look for? Thanks!