To gain access to the Extra 1 option on the main menu, you must first complete the Beginner's, Medium, and High Speed Classes in Championship mode. I'm not sure exactly what the requirements, cup-wise (gold, silver, bronze), are though; I had all Golds on all tracks when I opened up this options.
Hold the L and R buttons, then press Down/Right + B.
At the password screen: Complete each of the races with a gold medal
Enter the following codes at the startup screen (where it says Press Start):
- To unlock the Indy Car Mode, Press and Hold L+R, then press Left on the D-
Pad, then press B. When you hear a sound press start and it will be unlocked.
- To unlock the Go Kart Mode, Press and Hold L+R, then press Right on the
D-Pad, then press B. When you hear a sound press start and it will be
unlocked.
- For all tuning parts, press and hold L+R then Down+Right (diagonal) then
press B.
At the password screen, enter the appropriate password (case-sensitive):
Enter the following code at the Press Start screen....
Hold L + R and Press Up/Left + B
Then all of the cars should be unlocked
On the title screen (where it says ''Press Start'')
Hold both L & R shoulders, then hold diagonal Up,Right
then press B.
There should be a sound. Now go to Quick race and all tracks should be available.
At the main menu, press and hold L and R, then press Down, Right and B simutaneously. This will give you all car tune-ups in the game.
Complete the following tracks with a gold medal to unlock these parts.
Complete the final race in the professional class to unlock a seat which boosts all three stats.