What is a mod valve on the tranny?
What kind of transmission do you have?
On small/medium trucks, the vacuum hole on the intake would have gone directly to the standard/stock vacuum wiper motor. With a dual-action fuel pump, that vacuum line would have gone into the "in" port on the bottom chamber of a dual-action fuel pump. Or, if the truck has an electric wiper motor, that vacuum-line hole on the intake manifold would have been plugged.
