I think you misunderstood my question. How do I troubleshoot/diagnose/confirm what my failure mode is?
...To check Booster Chamber for a Leak. Attach Vacuum Gauge to Intake Manifold, Start Engine and Let Idle. Record Gauge Reading. From the Manifold, Pinch-Off the Vacuum Hose Leading to the Brake Booster. Note the Vacuum Gauge Reading. If there is NO Change, There is No Leak. If the Reading Rises, Even So Slightly...You Have a Leak! To Confirm...Release the 'Pinch' and Witness the Reading FALL, Momentarily (Vacuuming the Hose Out). If the gauge reading does Not Rise Back to the Previous High, there Is a Leak This Procedure will Also, check the Entire Length of that Hose, For Leaks. Or Pinch the Hose Off AT The Booster, to Check Only the Booster.