Dear Gary, Greetings from The Bronx!  Your problem basically stems
from the plastic valve blocks.  The design was originally conceived
from the Ampico unit valve blocks.  (AMPICO = American Piano Company,
which later combined with Aeolian Co. to form The Aeolian-American
Corp.)

Originally, when the plastic valve units were created, the valves
were made with a wooden disc with felt/leather facings.  Then someone
in their infinite wisdom replaced the felt/leather disc with a single
punching of neoprene foam.  When they are new the neoprene valve units
work perfectly, but as they age, the neoprene foam dries out, becomes
brittle and will slowly disintegrate thus creating a myriad of leaks
(multiply that by 80+ valves).  The drying out of the neoprene is
inevitable as it is surrounded by the lower section of the player,
and the main culprit is the ozone that is emitted by the vacuum motor.

There is someone manufacturing replacement valves which use the
original design using the wooden disc with a felt/leather facing.
These can be a bit pricey, especially if you were to replace all 80+
valve units.  Or you can go with the neoprene design, Player Piano Co.,
APSCO or Schaff.

The vacuum unit has four sealed plastic valve units attached to
a cast metal manifold.  The valves are paired and create a total of
three stages of volume in addition to the slide valve governor that
is mechanically connected to the vacuum reservoir.  Get a vacuum gage
and check the vacuum level first at the vacuum box and then at the
pneumatic stack and the tracker bar.  Experiment with the volume
control dial in the spoolbox.  More than likely you will find that
the vacuum box is putting out a sufficient vacuum supply at the box
itself.

Hope this helps,
Dale F. Rowe