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.
It appears that the Moon repeats certain phases: there are two crescent, gibbous, and half phases each month (each cycle). These phases are not exactly identical, however. Look closely at the diagram. You will notice that during phases 1 through 5, the amount of lighted area increases over time from right to left.he diagram above shows what the different phases of the Moon would look like as seen from Earth (note that the numbers below each phase correspond to the different positions of the Moon as seen in the first diagram).