Looks good!.
However the Front bumper, and some parts of the sideskirt and rearbumper is quite Toony to be honest.
Along with some poor selections on the Frontbumper. For example The Right sidevent (the one next to the Big middle vent) has a bad flow with the "innergoing" part (the part thats inside the bumper) Also there might be too much Grillemesh would look quite more cool if you had put, Lets say an intercooler with pipes on the vents next to the big Vent! imo.
If we go over to the roof it is tbh Very toony aswell, also the Frontwindow Border is toony.
However i believe this could be fixed quite easily by just selecting the light area (the bright red that is) And making a new layer and taking a brush at say 100px (depending on your Image size) Then take the eyedropper tool and picking a bright blue colour from the sky, and just smoothly make about half the roof a bit brighter (should get brighter the closer the Darkpart you get.
A tip; if the bg would have been brighter and you are going to do this, you might want to make another layer "ontop of the one we just made" and taking a 30 - 45px White Brush and just adding a fine line

It will look loads better i believe.
Now if we go over to your brushing, i think you can see for yourself it doesn't look quite Correct. If you look at the Colour of the body then the colour of the Bodykit you have brushed you'll see that It has a more "pink" colour also the black colour looks the sameway. although almost everyone but the Eliteextremeultramofochoppers have somewhat of a problem with this and its really not that big of a deal, unless its like a red car then having "pig pink" bodykit. That would just look wrong.
The wheels look good! Not so off as i can see, Love the camber <3 hah
The bg change looks great although the shadow coulda been alot better!
I know this might sound a bit harsh but this is what you need to hear to get better! and i tried to give you as much tips/tricks as possible, now bare in mind what i've said. And make an even better chop!
But overall the chop is acctually quite good, you have compiled a nice Style!
Good work ! now keep it up.!
