Roadster:
Defeat the Roadster in face off mode to unlock it and another face off race against another car.

Face off mode:
Successfully complete championship mode once to unlock face off mode against the Roadster.

Towtruck:
Play in championship mode until you unlock Face Off number 2 in the special options screen. Defeat the Towtruck once to unlock it.

Increase boost:
Drive on the wrong side of the road to keep increasing your boost. This can also be done by driving in the center of a double lane

Ending bonuses:
Successfully complete the game to unlock the Free Run mode (no vehicles on the road), Free Run Twin mode (two player Free Run), and "Credits" options.