Abstract: An automotive engine induction system has a throttle body and a manifold made of plastic composite material joined together by sliding a cylindrical sleeve extending from the throttle body into an opening in the manifold. Two lugs on the throttle body engage keyed slots on the manifold to provide positive angular and linear alignment, and two O-rings between the throttle and manifold seal the joint. A U-shaped pin fits through holes in the keyed slots to hold the lugs therein and snaps into a retainer clip incorporated on either the manifold or throttle body, thus providing an unstressed joint not susceptible to load relaxation of the sealing surface.