The Free Challenge Pack Add-on for Project Gotham Racing 4 has 7 achievements worth 80 gamerscore.
Earn more kudos than anyone else in a Tourist event
Be a cat on the winning team in a Cat and Mouse Open Event
Be a mouse on the winning team in a Cat and Mouse Open Event
Activate one of the cheats in the cheat menu
Try to qualify for a tournament
Puzzle #4
Puzzle #5