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.
Within one or two months, your vine should measure 6 to 10 feet and your first moonflowers should bloom. The first flowers will be small -- 3 to 5 inches across -- but eventually your moonflowers should measure up to 6 inches across. By late June or early July, the plant should be covered with blooms. Moonflowers may take five or six months to bloom after planting, which is why you should plant the seeds in late February or early March. Gather ripe seed pods after they turn brown, beginning in October.