2X prize money: 
At the main menu press:
L, R , Z, L, R, Z, L + R.

Unlimited turbos & shields:
At the Press Start screen press:
L + R, Z, L + R, Z.

Unlimited ammunition: 
At the Press Start screen press:
L, R, L, R, L + R, Z. 

Extreme lap challenge: 
At the main menu press: L, R, L, R,
L, R, Z, L + R.

All tracks & teams: 
At the Press Start screen press:
L, L, R, R, Z, Z, L + R + Z.