GTI Cup was designed for all 1975-1984 VW Rabbit/GTI models. The intent of this racing class is to provide an affordable (around $3000 car cost) racing series with cars that have limited modifications and "spec" components in order to provide close competition, limited expenses, and positive exposure. This is perhaps one of the least expensive ways to go racing.
For more information, see the official website:
http://home.infostations.net/GTICup/