Unlock Honda S2000:
Finish quest mode and Honda S2000 will be available to buy when you
start a new game.
Unlock Porsche 911:
Finish quest mode twice and Porsche 911 will be available to buy when
you start a new game.
Never Lose Kudos:
When you about to lose in a race, press A, B, X, Y, and Start at the
same time so that you will go to the title screen. Go back to your
last save and you will have the same kudos as before. Don't try this
during the second stage in a championship race.
Sites: