Cool, nobody posts these photochops up! I'll be a little bit picky to help you improve but I'll start by saying I like it.

I see two things:
-The wheels look low-res compared to the car or grainy
-The big thing I see is that when you make your selections you shouldnt use the polygon selection or w/e because it leaves sharp edges and straight lines. Try using the pen tool to make selections, it takes getting used to but it works alot better.