Profile: Hemco Machine Company, Inc. is a full service machine company for prototype machining, automotive computer electrical components and fixturing of all types. Our products include plates welded on an angle inside a stock plenum cover, poured epoxy liners in a stock plenum cover and machined billet plenum covers. The Hemco plenum cover incorporates a radius curve of 90-degree turn, cast into the plenum cover, with a specially shaped opening into the intake manifold. This design causes the intake manifold to react as if a throttle body was sitting on the top of it and increases the total CFM airflow even through a stock throttle body.