An intake manifold adapter comprising an adaper body made of aluminum and having a gas channel adapted to communicate at its one end with the outlet of a throttle body for holding an air cleaner in communication with an intake manifold and at the other end thereof with the inlet of the manifold, and an exhaust gas inlet pipe having an aluminum portion at its one end and a stainless steel portion secured thereto and providing the other end of the pipe, the inlet pipe being fixed to the adapter body by the aluminum portion being metallurgically joined to the body, the stainless steel portion providing a joint for a pipe for returning the exhaust gas from an engine to the manifold.