Dear Joe,  One thing that I haven't seen mentioned: The suction applied
to the valves may be insufficient in the first place.  The valves are
supplied by suction that is adjusted by the Brilliant/Normal/Soft
switch.  If you have your settings low because your room is small, or
whatever reason, and you have any or all of the problems that have been
discussed, you may get sluggish response.  You may have to sacrifice
more volume for better response.

Test this condition by setting suction as high as possible and then
open and close the loud and soft pedal ports.  If they work well at
high volume but poorly at low volume, that's your problem.

It would be nice if Ampico drew suction before it was regulated, but
they didn't.  Was it a design problem?  I don't think so; after all,
it worked well for many years.

Good luck in searching for your cure.  Let us all know what you find.

Jeff Davis, in sultry Seattle