Unlock Climax Mode
When the menu screen appears just enter the code while holding the two shoulder buttons. You must do it within several seconds of the menu screen showing up and you will hear a noise. If you mess up you need to either restart the game or go into a race and go back to the menu.
[Up], [Down], [Up], [Down], [Up], [Down], [Up], [Down], [Up], [Down], [A] - Unlock Climax Mode