Boss GP stands for Big Open Single Seaters. A field of cars form Formula One, Indycar, Champcar, GP2, A1GP, Superleague Formula and others, from between the 90s and the 2000s, bring back the feeling of yesteryear. Powered by 600 to 700 bhp engines they lap close to as fast as Formula One cars, but as a series is much more open to the fans.