Press UP, Down, Left, Right at the main menu to enter the code entry screen. Then enter one of the following codes.
Madaza RX-8: enter RENESIS as a code
99 Mitsubishi Eclipes GS-T: IGOTGST as a code (in arcard mode)
Police Warning instead of ticket: enter LETMEGO as a code. The first three times you are pulled over in street mode, you will be released with a warning.