Black Box Classic Car:
To unlock the Black Box Classic car beat the Short Track Challenge.
Black Box Exotic Car:
To unlock the Black Box Exotic car beat the Half Season.
EA Sports Car:
To unlock the EA Sports car win the Road Course Challenge.
Beat the Superspeedway Shootout under either veteran or legend difficulty.
Play as Asher Boldt:
Go to the credits and select (development) when the credits role put this
in as a code hold L2 and press Square, Circle, Triangle, and then X.
Treasure Island Track:
Beat a season under the veteran difficulty setting.
John Andretti's Second Car:
Select "Credits", then "Development" at the options menu. Wait for the FMV
sequence to complete, then hold R1 and press Square, Triangle, Square, Triangle
when the credits begin to roll.
Proving Grounds Track:
Select "Credits", then "Developers" at the options menu. Wait for the FMV
sequence to complete, then hold R1 and press Left, Circle, Down, Right,
Start On Lap 2
Thanks to Revolution readers Benny, Gamefreak and ~MaTT~!