well, first there is an odd dark area get rid of that. Then, you have to think about sunlight- what is there??

1. Very strong point light. This should be faked using a spot light with 179.999 angle though, since that eliminates extra time for photon casting and whatnot that point lihgt should use. This light is a touch yellow, but very bright. Tweak light/photon settings accordingly

2. The ambient area light of the sky. I don't know how you would do this, I would use a skydome, but a solid sky blue colored JPG env map would work. This would be, i don't know, 1/4 of the overall light>? possibly 1/2?

Next point- the actual car shader. The metallic paint is obviously CG because it is so plastic. It seems that in Maya it is easy to get a nice looking plastic, much more challenging to make it a metal. I would turn specularity up, but a specular map in some areas for dust and whatnot would work. Also try to dust up the color map too

That's all I could think about now, hope it helps