The present invention provides an improved bonding system including an adhesion promoter that may be used to help adhesively bond two or more components together. The preferred use of the present adhesion promoter is in a transportation vehicle (e.g., automobile), and more particularly in an engine assembly for use in such vehicles. The present invention includes a bonded automobile engine assembly including at least one plastic component, an adhesive that bonds the plastic component to at least one separate component, and an adhesion promoter between the adhesive and the plastic component. Fasteners for attaching components are optionally employed. In one specific example, an intake manifold including a plastic component is bonded to an engine assembly.