Holley Modular Lo-Ram EFI Manifold LS1/2/6The 300 620 plenum entry configuration is designed to allow the included Hi Ram 105 mm plenum top to be fitted to a low profile base intake manifold. The short runner, low profile base intake manifold intended for forced induction applications was conceived to package with an air to water plenum mounted intercooler with a shorter overall height than possible with other existing intake manifolds.