The tuner car is, by definition of Wikipedia.org, is both an industry and a "Hobby" in which a car is modified in order to improve its performance and handling and improve the owner's driving style.  It is a popular topic in street racing movies like the fast and the furious movies, gone in 60 seconds, and Knight Rider the TV series.  These cars are fast, usually built to the owner’s wants and styles and have an infinite amount of possibilities. For instance, there are even some police cruisers, known as “Sleepers” that may just have internal modification done to them so that they can be of use in extreme high-speed chases.  Effects include but not limited to items like spoilers, hood scoops, side skirts, underbody lighting, NOS (nitrous oxide systems) and sound systems that cause heads to turn.  Some popular cars to modify include the Mitsubishi Lancer and Eclipse, Subaru Impress WRC STI, and Toyota Supra.

 

 
Mitsubishi Eclipse Ralliart
Mitsubishi Lancer Ralliart
Toyota Supra
Subaru Impreza WRX STI