When the Red Bull Air Race began back in 2003, pilots competed in several different aircraft. Paul Bonhomme explained that it was a "run what you brung" set up. This meant whatever was in your hangar at the time was competitive enough to be flown in the Air Race.
It's a completely different story now. Pilots are backed by structured teams. The race hangars are full of tacticians, aerodynamicists and technicians all trying to discover a new way of shaving time off the pilot's run.