Brake Pedal Diagnostics

there's so many possibilities here. the pedal generally drops a little once the car is on but excessive travel or sponginess is not acceptable.

if you haven't already, make sure that your rear brakes are adjusted properly. double check the bleed and make sure you have zero-point-zero air in the lines (this is probably the most common culprit, after leaks in the system). as dana mentioned, the master could be bypassing, this is common on a master with bad cup seals and seals can go bad from sitting. unless it's puking fluid out the back, then it's definitely the master. lastly, i'd suspect the booster.

thankfully most of those checks are easy, quick and free.