Vacuum in the manifold drops as engine demand increases. If you use ported vacuum you always have a vacuum signal. If you want to make adjustments it can be done using the advance pot on the distributor when you use ported vacuum.
The decreasing or waning phases are when the moon shrinks from the full moon down to the new moon (darkness). As the moon wanes during the 3rd and 4th quarters, this is a good time to prune plants, as the water table is diminishing and so less sap will flow out of the cut ends.
The term  moon cycle  (or lunar cycle) refers to the moon's continuous orbit around the earth. As the moon orbits the earth, its appearance (the phase) changes and thus gives us an indication of the moon's progress in the cycle (the age).This complete lunar cycle (New Moon to New Moon) is also called a lunation.During this time the moon will completely circle the earth. That's the scientific definition, but you can take any phase; for instance a so-called full moon cycle would be from Full Moon to Full Moon.s the moon orbits the earth, its appearance (the phase) changes and thus gives us an indication of the moon's progress in the cycle (the age). This complete lunar cycle (New Moon to New Moon) is also called a lunation. During this time the moon will completely circle the earth.