At the options menu, hold R1 + R2 and press Up, Left, Right, Down, Triangle, Circle, X.
At the car and item selection screen, hold L2 + R2 and press Left(2), Right(2), Square(2), Circle(2). If you entered the code correctly, you will hear a sound.
Pause the game, then hold R1 + R2 and press Down(3), Circle(3).
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