Getting air into an engine to mix with fuel is the holy grail of speed, and HTM Motorsport turned to Stratasys to help them design and built a lighter, more efficient airbox for their BRC-14 student race car. The novel design and materials used in the project gave the car a 10% percent boost in horsepower and a 12% increase in available torque. The airbox was built with Stratasys Digital ABS material for its toughness, performance and fine finish characteristics. You can read the whole story here: http://3dprint.com/54129/3d-printing-htw-motorsport/
Below is a photo of the 3D printed parts for the airbox: