Back to your original post of Porsche. Sorry to jump in so late, but just saw it.
(1). Very little Gaussian blur & small motion blur of background should enhance the car. Also reduce the brightness level of background.
(2). Add truncated headlights trails with grain, opacity & edge fades.
But overall it is a very nice feel of what you have done. that is just my 2c, just a different modified look.