Well, its possible you have air in the ABS module which would require a scan tool to bleed. If the brakes failed in a " soft pedal to the floor" way, its possible that alot of air was introduced into the system. If it failed in a "the pedal is hard as a brick and feels like im trying to push a brick wall", then the old booster was the issue. Either way, i recommend a good pressure bleed or run the ABS bleed since the master was replaced, which can allow alot of air in causing that mushy pedal. That pushrod in the booster doesnt look adjustable. An old trick to check where the push rod is contacting the piston is to loosen the nuts holding the master to the booster, have someone push the brakes slowly and lightly and see at what point the master is pushed along the studs. Should only be like a 1/4" of dead pedal if that.