I have a lot of pedal travel on the first pump of the brakes, sometimes the brakes barely work at all with one pump. On the second pump the pedal feels normal like there is no problem.
Here's what the car has that are known good parts:
new super blue brake fluid (bled by myself and confirmed by my shop that there is no air in the line)
All parts have been checked with a caliper and are within spec, the rotors easily exceed minimum thickness. There is no vibration in the braking, just too much pedal travel. When I get pressure built up the brakes feel good and stiff and there is no loss of pressure so I believe my brake booster is working properly. All signs point to the master cylinder at this point, but I'd like to know if there is a way I can test it before I just buy another one. Thanks