Power Disc Brakes not working on hard stop?

OK quick up date, I purchased a new brake booster from Summit RSD- RPB8001, believe its same one classic industries sell - look identical. Anyway I installed and now problem is worse. I have a rock hard pedal with no assist. I check vacuum and power booster canister holds 21 PSI vacuum for 20 minutes - Summit's test for good booster. With the old booster I had power assist but ran into rock hard pedal and limited braking. Braking feels the same without power assist now. $225 down the drain and worse off.