Bonus Tracks: 
Successfully complete practice mode under the beginner, intermediate, and expert difficulty settings to unlock new tracks. 

Bonus Cars:
Defeat each driver in story mode to unlock a new car. Three more cars will be unlocked when story mode is successfully completed. Five more cars will be unlocked when story mode is completed a second time. One more car will be awarded when story mode is completed a third time. The final bonus car is awarded when finishing first in D-Check mode. 

Unlock Bunta's car, the GC8V: 
To unlock Bunta's car for use in Arcade or Time Attack mode, defeat Bunta in Story Mode (Stage 31). After beating him, the GC8V will be available in car manufacturer section under Subaru. 

By the way, this car only has one default tune option, and it only comes in one colour. 

Buntas IMPERAZ:
At th car select menu you enter the folowing Down,down,up,up,down,up,down,up, hold in brake and then view change.