I wanted to share some code I whipped up to improve upon the built-in car behavior. One thing that seemed to be lacking was the fact that after letting up on the throttle, the car would drift for a long time as if it was on a near-frictionless surface. There is a friction setting in the car behavior, but it only seems to be applied to collisions with solid objects. The other thing I changed was to allow the car to pivot to the right or left, even if the car's speed is 0. Here is the even sheet I used, along with the behavior properties I used:
<img src="http://i39.tinypic.com/eq9u1.jpg" border="0" />
<img src="http://i41.tinypic.com/24dofpi.jpg" border="0" />
If anyone has discovered an easier way to implement these things, please let me know....otherwise, enjoy!