It is tired and wants to be swapped out with a vacuum or hydro set up.Get rid of the power master.I am sure you read about be wrecking my car when mine went out.
just ask for a na regal booster and master cylinder and don't forget you need to get the brake pedal from a na car aswell. if you go to the junk yard and pull one from any g body its only about 50.00 for the whole setup.