I have been reading the various suggestions to remedy the sluggish
Ampico Pedal pneumatic, but so far no one has mentioned the bleed in
the unit valve controlling the pedal pneumatic might be plugged with
dust.

Remove the two valves, and check the one that has the bleed to see
that it is clean.  While the valves are out, also check them for pouch
leakage.  In addition, the wooden valve laminations are very prone to
split and begin to separate and leak under the tension from the stiff
clamp "Spring" holding the valves in place.  Check the sides of the
unit valves, look for cracks.  Small cracks are hardly visible, and
should be sealed with burnt shellac.  In severe cases, I have seen the
Bakelite valve seat distorted and ruined by excess "clamping".

Another problem is pre-made cork-rubber unit valve gaskets.  The rubber
eventually gets hard and can cause leakage.  I prefer plain cork gaskets
that are very easy and inexpensive to make.

I advise all Ampico model "A" owners to replace original stiff metal
"springs" with the later model "B" type flexible spring which will
allow slight expansion and contraction that occur during a wide range
of percentages in humidity.  Keeping the old "springs" is inviting the
eventual destruction of the unit valve, because there is no room for
expansion.  In other words, if the wood in the valve expands, and the
original stiff metal clamp (spring) will not move, the unit valve will
eventually distort itself and be crushed by being held in place too
firmly.

In regard to the possibility the modify switch might be the cause the
problem, a better understanding of this switch is needed.  The modify
switch does not increase or decrease the pump pressure at the moment it
is set, and the air motor governor and other vacuum regulated devices
are not under "Expression" (regulated) by the expression system or
modify switch.

When the modify switch is set at soft, a separate device (re-regulator)
block the suction from the pump and limits it to not more than 12" of
vacuum supplied to the stack.

Subdue: or soft setting: limits expression from 6" of vacuum to the top
level of 12"

When the modify switch is set at medium, it actually does nothing but
allow the pump to run a normal pump spill valve setting: no more than
20" of vacuum.  (There are no hoses going to or from the modify switch
for the medium setting.)

Medium: 6" of vacuum and up, to no more than 20"

When the modify switch is set at brilliant, it opens one tube that goes
to the amplifier control box, and allows the pump to increase the spill
valve setting by about 10" additional vacuum when called for by the
expression system.  The expression system is activated from the roll
code.

Brilliant:  6" of vacuum and up to no more than 30"

Anything above 6" of vacuum is called for by the expression codes in the
roll.

Bruce Clark