The pedal is hard, plus I can't lock the brakes up. Actually, the car brakes OK around town, but no matter how hard I push on the pedal, I can't lock the brakes. With discs up front, I figure should be able to lock them up.If your brake booster is bad, I would think you would have a hard pedal.
Also, if your booster is good, it will hold vacuum for a long time, providing the check valve and grommet are good. Pull the check valve out of the grommet in the booster, you should hear the air rush in.
The brake pedal rod has to be adjusted correctly for it to work properly also.