The evolution of materials technology has provided in recent decades the replacement of the raw material of many parts made of metal by polymers, carbon fibers, ceramics, and composite materials. This process has been driven by the permanent need to reduce weight and costs, which, even after replacing raw materials, still demand permanent improvement and optimization in the sizing process and in the manufacturing process. In the automotive industry, many components have been replaced by fiber-reinforced polymers, from finishing parts to structural components that are highly mechanically stressed and often also subjected to high temperatures. Although they are lighter and have a lower final cost than conventional metallic parts, components made of fiber-reinforced polymers bring great technological challenges to the development project. Within this context, computational modeling is an indispensable ally for obtaining a product capable of meeting the severe conditions required for its service. Peripheral engine components such as air, oil and fuel filters, canisters, valve covers and intake manifolds are examples of components that are commonly made of fiber reinforced polymers, but that present relevant thermo-mechanical and vibrational requests. The simulation of the polymer injection process and its coupling to structural modeling is a crucial differential in the development of these products. The consideration of the anisotropy caused by the reinforcing fibers in the polymer has a very relevant impact in terms of stresses and strains, as well as the stiffness of these components. The fiber alignment that defines the anisotropy in the part is obtained from the simulation of the injection process and introduced in the finite element model that will be used for structural evaluation of the component. Aiming to illustrate the relevance of this anisotropic structural modeling approach, which couples the manufacturing process with structural simulation, two case studies are presented: a fuel filter subjected to rupture test comparing numerical and experimental results and the second case is the natural frequency analysis and vibration modes of a valve cover.