The p/n for the gauge is SUM-800160 and you'll need an adapter fitting p/n ATM-3280.
I think I've got a bad regulator. With the vac unhooked I can set it right at 38#. When I hook up the vac it drops to 28-29#. It will spike up to 32-34# when I rev up the motor.
I have not tried to adjust...