Ok let me try to give you a little feed back (I am a REALLY good A-hole:mrgreen
Use a little lighter black and a grayer white to start with; because the colors will have been faded from the factory.
Add high lights and shadows: Add depth with the dodge and burn tools along where there are ridges and valleys on the real life vehicle.
Make her a dirty girl: you need some weather (mostly along the hood section and also on the panels behind the wheels) some dirt maybe even some chips
Oh and also use a noise filter to grunge it up.
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You have a good base though so keep at it.