Challenge Pack - Free
You can either do this legit or boosting, just start up any 'Cat And Mouse' race on an open event with you as the cat and win the race.
Cat and mouse has two teams, the cat and the mice. As a cat you must ram the mice who will attempt to run away from you. Ramming a mouse will give you around 400,000 thousand points every time. Try to get the mouse into a corner or up against a wall so you can hit them multiple times before they can escape.