Play with lighting/angles/exposure a bit. You've got primarily dark cars in dark environments. That can look really good when you can see details. Either place the cars in a more well lit area or up the exposure value a bit.
Also in a few shots, you've got really highly exposed areas(windshields) along with much less exposed areas like the sides of the cars. That contrast makes the details of the body of the cars harder to see.
Dark pics can be great, but they either have to convey a certain mood or story or they turn into just really dark pics.
Play around with light a bit and these turn into much better shots. That being said, I really like the way your GT-R Spec looks. Post more soon.