I saw your California Drifter post. When you got over 15k on that one lap, did you cross the finish line, hit the menu, and then exit the event? I've been reading that you need to that to pop the achievement.
Also, do you have any tips on how to get ~1800 points per turn? I'm not sure if I'm using the brakes and gas properly, as you can see in my post above yours on the thread.