Unlimited shields and turbo's:

At the main menu, hit L1 + R1 (at the same time), 
then L2 + R2, L1 + L2, then R1 + R2. This should
display a message saying unlimited energy. Start
your game, but you will also get unlimited turbos
once weapons and boost are activated after start.

Note: The code has to be re-entered for each race.