Funny to be reading this becuase I have the same exact problem. I can say without much doubt that it is the booster. My car had the same symptoms and I replaced the booster and they went away. If you listen closely you should hear a hiss with the pedal depressed. But just yesterday I replaced the front calipers and rotors and master cylinder and after I had bled the master cylinder and all the calipers the booster had once again died. So today I replaced it with another junkyard booster... and of course it's no good and I'm back to where I started. So I can safely say that its the booster BUT check the check valve and seal first because they are cheaper to replace than the entire booster, plus they can be had at autozone I know for sure. Also if you get a junkyard booster make sure its good.


Good luck to you (and me). Adam.