Here are some.
Increase License Level
To increase the level on your license, you have to win championship titles in Career Mode.
Win the 2.0L championship twice and you'll get a 'Level2' license which allows you to drive higher performance cars in the Single Race mode.
Win the 2.0L championship four times in total and you'll get a 'Level3' license allowing you to drive at Performance Level 3 in Single Race mode.
Contributed By: Chicken McNuggets, Source: Self
Unlock Bonus Cars
To unlock the four bonus cars in the game you'll need to do the following:
Subaru Impreza 2000
- Win the 2.0L Championship in Career Mode.
Mitsubishi Lancer Evolution VI
- Win the 1.6L Championship in Career Mode.
SEAT Cordoba Repsol
- Complete Challenge Mode.
Toyota Corolla V-Rally
- Set record time for all circuits.
Contributed By: Chicken McNuggets, Source: Self