Get in front of the pace car
To get in front of the pace car, you must set the pit mode to normal and yellow flags on, go to the track and cause a yellow, when the yellow flag comes out, pit, but hit abort when entering the pits and if it does not work, pit again if you are in the back of the field you will not get in front of the pace car, but you will gain some positions. (Works with any car on any track, but be careful sometimes they hold you in pit lane.)

Treasure Island track
Win a season on the veteran difficulty setting.

Black Box Classic car
Win the Short Track Challenge to unlock the Black Box Classic car.

Black Box Exotic car
Win the Half Season to unlock the Black Box Exotic car.

EA Sports car
Win the Road Course Challenge to unlock the EA Sports car.

EA.com car
Win the Superspeedway Shootout on either the veteran or legend difficulty settings.