3. In a conventional dual- or single-plane intake manifold, vacuum accessories often pick up their vacuum signal by tapping into the plenum. Since an individual-runner intake manifold doesn’t have a common plenum, vacuum is picked up off of the bottom of each runner. Brass fittings from the runners hook up to a centrally mounted distribution block using -6AN hoses. From the block, vacuum can be distributed to accessories such as the distributor or brakes.