air in the lines to me would be a mushy pedal, or no pedal at all.
I have a rock hard pedal. I cannot push it past a certain point.
I have verified with the master removed from the booster, I can move it past that point.

now I have to see if opening a bleeder will let me move it past that point.

if not I guess bad master.
if it does, then I am still not sure where to look, but at least I know it isn't the 2 of those items lol.

I checked both calipers move freely. not sure where else it could be bound up. but I will get there once I eliminate the master.