To unlock other cars, you need to find three keys per
level. When you begin a level, it is a good idea to find all the
keys, then complete the laps. It does not matter what you place
when you are looking for keys; take your time, and complete the
level. If you do not complete the level and found all the keys,
do not worry -- you still get the prize. However to go onto the
next level, you must place third or higher.
In the third Grand Prix, in the second to last level "Tomb
And Gloom" is where you can unlock the find fastest car once
you have found all the keys. The third and last key is hidden
well here. It is in a curtain draped off the ground in a descending
matter (just hop of the ledge onto the curtain). A good rule of
thumb when looking for keys is to change the cars view to a more
elevated position, then try to spot the sparkling keys in the
distance.
Trainer: All cars, tracks, and championships unlocked by TNT