Man, those are great!
1st one is my favorite, though. It's so clean it hurts my eyes...
Very nice job with the black car color, came out beautiful, not washed out and not too black.
The FTO looks pretty sweet too, very impressive.
Have you tried applying dirt along the part where the Bridgestone logo is in the front? it's an area that would usually be dirty, due to aerodynamics, and it would probably enhance the dirt on the lower part of the bumper.
As it is, the dirt you did appears to be more of a shadow on those areas, but it still works fine. Just my thoughts, amazing work, nevertheless.
Oh, and... DO THE TUTORIAL!!!!