Abstract: An apparatus and method for incorporating a plurality of various fuel and emission components generally located on the top or outside of an internal combustion engine into a completed sub-assembly that can be delivered to an engine assembly line and installed as a unit on the engine. The air-fuel system components are assembled in a unitized or integrated air-fuel module which is then assembled to the engine. Also disclosed is a method of assembling an engine including providing an intake manifold base having at least one valve cover integrally molded in a bottom of the intake manifold base and having integral intake manifold runners; assembling an integrated air-fuel module at a first location; and then attaching the integrated air-fuel module to the engine at a second location.