This intake manifold gasket seals the joint between the intake manifold and the cylinder head on the host engine. It prevents unmetered air from entering the intake stream, which would disrupt the air-fuel ratio and reduce combustion efficiency. A failed gasket produces a lean-running condition, rough idle, and a drop in engine power. The gasket is manufactured to the original geometry so it matches the sealing surfaces of the manifold and head without additional modification. On reinstallation, clean both mating surfaces and tighten the manifold bolts in the sequence and to the torque value specified for the engine.