Successfully complete the indicated event(s) in the Challenge Series to 
unlock the car:

Aston Martin DB9 (Exotic)       :Defeat Wolf in Boss Battle mode.
Dodge Charger RT Classic(Muscle):Defeat the 21st Muscle Car Gang.
Jaguar XK 2007 (Exotic)         :Successfully complete all three Turf War races.
Mazda RX7 (Tuner)               :Defeat Kenji in Boss Battle mode.
Nissan 240SX (Tuner)            :Successfully complete all three Checkpoint challenges