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.
A new moon represents a new start for this month ahead, with the best time for initiating new projects and putting plans into action being the first two weeks. This is the waxing phase of this new moon cycle, up till the March 14 full moon. The new moon conjunct asteroid Chiron is both a positive and negative influence. It suggests some wounds will be opened up, but at the same time, it allows for the healing of these wounds.