Hi, my name is***** for the long wait on this question. If you have no power assist when driving the car and braking you will need to check the vacuum to the brake booster. If you have good vacuum to the booster you will probably need to replace the booster. The only other thing I can think of is you lost the o-ring on the end of the master cylinder when you removed it. If the o-ring is missing you will not have power assist.
Let me know what you find.