Intake Manifold Gasket Seals the Intake Manifold and the Cylinder Head. Leaking gaskets can cause erratic idle and performance issues. Replacement is also recommended when changing the intake manifold or removing and refitting the intake manifold. Expect unrivalled Japanese quality and a first time fit for the application. Sourced directly from Japan. I purchased this about 3 months ago from RHD, my customer K20 build is no longer going ahead. So selling everything I purchased for it.