Hi. I already changed the booster and master cyl. Everything went fine for a year and 12,000 miles. How strange behavior, seems like I am losing brake vacuum. When at a stop, the brakes have almost no continued grab. Car starts creeping. When moving, I have hard breaking but not soft braking. Even hard braking is not like it was but will stop the car. But the first inch of peddle does very little. When I pulled the one-way valve out of the booster, there was vacuum in the booster (light hiss--even with engine off). Plenty of brake fluid. 1998 2.7 base 64-k miles. Stumped. Thanks.