There just a unbolt and rebolt on the booster, fairly simple
Before you bought said suspect part, had you done a complete visual for any suspect leak/leaks/sepage ???
A shorty here had the dreaded brakes one pump,not the other syndrome
It was a bend in a line,(that ended up eventually breaking) few pumps hold pressure, then drop once pressure was released and tried again
Replacement brake line fixed that
Anywho you have the new master cylinder now,mite as well fit it,and do a full system bleed