Super Blurry Mode
To experience what Boss Games calls "Blurry Assed Graphics", enter
the following button combination with the second controller during
normal gameplay:
B, Left, Up, Right, Right, Right, A, Start, Start, Z, Right, A, Up, Z, Bottom-
C, Start.
Note: Use the D-Pad for the directional commands.

Midway Code (Red Skid Marks)
While racing, press the following buttons (use the D-pad for this code):
B, Left, Up, Down, Right 3 times, and Down. If used correctly, you start
seeing red skid marks instead of the black ones.

Top Down Racing
Enter the following code while you're racing: Up, Up, Up, A, Left, A, A, A
This puts the game into a top-down mode, that's a lot like the old arcade
racers of yore.

Infinite Restart Credits
Enter the following code while you're racing: Z, Right, Z, Right, Right,
Start, Z, A, Right, Z, Start.

This will set your restart credits to 9 -- and they will never go down.
Note that when you save and then restore the game, this cheat will be
reset. If you want unlimited restarts again, just enter the code one more
time.

Drive 2000 Falcon Interceptor
To drive the 2000 Falcon Interceptor, you must win all racing events.
Then race the Novice Cup and defeat the Interceptor in the Novice Cup
races. The Interceptor will become a staple of the Boss Racing Team!

GT2 Ending Sequence
To unlock GT2 Ending Sequence option, successfully complete a GT2
season.

Unlock Sydney Circuits
To unlock the last GT1 circuit (Sydney) and all of its variations WITHOUT
saving it to the memory card, simply begin a Championship game and
enter “FROZENSKY” as a name.
To save Sydney Circuit cheat to a memory card, perform the following
steps:

Remove the memory card from the controller.
Start a new Championship game, entering “FROZENSKY” as the driver
name.
Accept an offer from one of the two race teams. (If you do not accept
either offer, the code will not work.)
Go back to the main menu and select Quick Race.
Choose a race mode and select the Sydney circuit.
Go back to the main menu and install your memory card.
Load a saved game.
Save the game.