In this publication, a method was developed for the production of plastic parts for the use in low volume automotive production. The hollow parts having a complex geometry were produced in blown plastic injection molds. The part production method employed a combination of carbon fiber reinforced composites and rapid prototyping technology. Surface operations were applied on the core model and the effects of the surface quality were researched as a case study. The fused deposition modeling method was used to build the core from soluble material. This technique affected the inside surface roughness and quality of the final parts. As these types of components require smooth surfaces for good air flow and low resistance, the surface area of the physical model of the soluble core was unfortunately too rough to be used directly in the carbon fabric application process and consequently, required preliminary surface treatment in order to improve the surface quality of the manifold part. Specimens were fabricated using different surface treatments in order to determine the smoothest surface quality. The best result was obtained using the acetone-gelcoat post-processing method.