lol, its not that you cant post process, its just that HDR can be too much. HDR is a trick art to master and definitely takes time to get the trick. Right now you've done more with it than I have, and they look good. It would just be nice to have some pics that arent HDR too.
Some quick edits (a little too much maybe)
With my car a very similar color and having the same wheels in the past I have some experience you might find useful taking pics. Our color tends to look very drab sometimes on cloudy days, ESPECIALLY with the bronze wheels. And this current set shows that a lot. Some things I did to help that. Added color to the car by putting the amber lights back in for turns. Also, if its doom and gloomy out, try to take pics in front of a more colorful back ground (brick wall, etc). Gives the car more contrast, and helps the camera distribute the tones a little better.
Anyways, more practice = better pics. You are framing your pics pretty well though