Nice to see you're still working on this one !
Nice use of Yaf(a)Ray, you have to improve the lighting quality because shadows under the car are really noisy at the moment. I'll post some settings I'm using later, if you need some help (which I doubt of

)
The outdoor render looks much nicer than studio ones : you have to complicate the studio setup a bit because the paint looks completely flat there. It has only two colors, one where it reflects a white plane and another where it doesn't.
A modeling critic : you should really add cover to your headlights.
Keep it up, this project is coming along really nicely !