Instructions
Select the "Settings" option from the main menu and change the difficulty level to "Hard."
Choose any car and play through "Story Mode." In Chapter 4, defeat "DJ, Wingo and Friends" in the "Delinquent Road Hazards" race, which comes after the race at "Tailfin Pass Circuit."
Finish the game's "Story Mode" and wait for the credits to stop rolling. Save your game.
Choose any car and select "Exhibition Mode" in the main menu. Choose the "Delinquent Road Hazards" circuit.
Finish the race in first place and exit to the main menu. DJ will now be unlocked.