Okay, maybe I don’t entirely know how brake boosters work, so maybe someone can tell me how I got here. ‘71 GTV, all original car. Rebuilt calipers, new soft lines, new MC, and I could not get it to have a firm pedal. Bench bled MC, bled four corners several times. Really squishy pedal, but the brakes did work, but only right at the floor. Not confidence inspiring. So, out of frustration, disconnected vacuum hose from booster and depressed pedal a few times. With a buddy holding his thumb over booster valve, pedal was super hard. Reconnected hose to booster a pedal is now firm. What was going on?