brake pedal to soft help!!

ok so it all started with me driving down the highway and the caliper seized up so i took the caliper off and rebuilt it then with it off i got new pads and rotors, then i replaced all the hard brake lines (they where old) i bleed it all and the pedal still feels really soft. so i next replaced all of the fallowing: booster, master cylinder, booster check valve, combo valve.(bleed it all also) and still the pedal is just as soft. so with the engine running if i hit the brakes all the way down the idle drops (pedal still soft when doing this), so i disconnect the vacuum line that goes to the booster and plug it and then the pedal feels much better, so what does it mean if it seems to work only with the vacuum line disconnected?

thanks
mike

When you step hard on the brakes while stopped, does the pedal hold steady or slowly continue to go to the floor? While driving, is you step faily firmly on the brakes, does it stop quickly without pulling? When you disconnect your vacuum line, you are taking away the power brakes.

the pedal comes back up but it takes nothing to push them down

Does it go down to the floor? Are you saying the brakes work good, but they are too easy?