High resolution mode
Earn an International A License, then enter the GT League and win all four cups, including the GT World Cup. Now you will get an extra menu in Special Events called GT Hi-Fi. This mode gives you better sound effects, boasts higher resolution, and smoother frame rate by reducing background details. You will also be the only one on the circuit (time trial), and you can view your replay in this mode.

Bonus cars, tracks, and more
Beat all tracks with each type of car (A, B, and C) on all three modes of difficulty (easy, normal, difficult). Then, this will enable all bonus items in arcade mode, which include four other tracks (Autumn Ring, Deep Forest, SSR5, and Grand Valley Speedway), all cars (Toyota, Subaru, Dodge, and TVR), a bonus ending FMV sequence, and high resolution mode.

Chrysler Copperhead concept car
Get all gold medals in the B Class license test. Alternatively, finish in first in the UK vs. US championship.

Toyota TRD3000GT
Get all gold medals in the A Class license test.

Nissan Nismo 400[R]
Get all gold medals in the International A license test.

Hidden FMV sequence
Select arcade mode, obtain all bonus tracks, then finish in first place on all tracks with any car. This must be done in A, B, and C class mode on the normal or higher difficulty setting. Then, a "Staff Video" option will appear under "Bonus Items".

Conserve memory card slots
Play the game in arcade mode, exit, then enter simulation mode and save the game. Now the arcade and simulation mode information will be saved together, cutting the amount of memory card slots used by half.

Memory card battle with one card
Enter memory card battle mode. Then, a message will appear stating that player one is loading and that no memory card was found for player two. Wait until the information has loaded for player one, then remove the memory card and insert it into the second memory card slot. Now the game will load data from that location and allow both players to participate in the memory card battle.

Duplicate parts
Buy two identical cars. They may be given different color schemes if desired. Then, buy as many parts as desired for the first car. Now view the list of fitted parts of the first car from the garage. Switch to the second car, get inside, and view its fitted parts list, which should be empty. While remaining in the second car, enter a spot race. At the qualify options, select "Machine Setting", then "Change Parts". All the parts from the first car should be available. Exit the race and return to the garage. Then, view the list of fitted parts for both cars, which all desired parts so now be duplicated.
Note: Only items available on the "Change Parts" menu may be duplicated. This trick will not work on cars that have been awarded.

Get Really Cool Cars
Oops, that's not possible in this game, sorry. (just kidding, I pick on all car games with the either the Copperhead, Prowler, or Viper)

Note: Activate this code, then turn the Game Shark off and enter Arcade mode, then turn the Game Shark back on. Also, if you save it to your memory card, you will not have to activate the code again. Same for the money and license codes.