If you keep tapping X when you are driving the vehicle will go faster without using the boost which will allow it to charge.

The following codes are entered by holding down all the indicated buttons and pushing the analog sticks in the direction which is required. If the code has been entered correctly you will hear a noise as confirmation.

Unlock Everything:
At the Main menu hold L1 + L2 + R1 + R2 + R3 (Analog sticks pushed Up) +L3 (Analog sticks pushed Down).

Unlock Big Head (ATVs and Bikes):
During gameplay pause the game and hold L1 + L2 + R1 + R2 + R3 (Analog sticks pushed Right) + L3 (Analog sticks pushed Left).