If you have a vacuum gauge, it would be beneficial to T into the line to the transmission and read the vacuum at idle. That line runs from the top of the vacuum amplifier (blue flying saucer).........the side port on the top.........

Or, you can just wing it. Remove the vacuum amplifier and you'll find an adjusting screw under the black plastic M/B cap on the bottom of the unit. Turn the plastic hex screw fully clockwise and reinstall the vacuum amplifer. You'll need a 4mm socket for this screw.......don't try it with anything else.

Take it for a drive and see how you like it.