again, like i just said in a different thread. You want the luminosity all the way up to eliminate the "halo" effect you see under the car. Also, you are probably trying a little too hard for that cartoonish effect... try medium smoothing instead (this is in reference to Jnic's rendition). Also, like I've said 1000 times, try using just 1 raw image especially when starting out with this program. more times than not you won't get the best result because you aren't bracketing properly. its not about being exactly at -2, 0, +2 for the shots... besides unless you are using a real light meter you aren't actually getting the perfect "0" exposure because you are measuring the light with the camera seen in the frame which can be wrong and distorted because of a black or white object in the photo.
Shoot raw, use 1 exposure to start off and work on getting 1 properly exposed picture rather than 3 or 5, let photomatix decide how it wants to bracket and your pics will look a lot better.