Great effort on the brush!
BUT, the car below it's own horizon line has a different shade of red than the rest of the car! Its less saturated and is way too toony! I also think the car is at angle which the BG doesn't match, the whole car is also too bright on the BG, the hood scoop is also slanted or just simply off, the bad boy look is not symetrical, they don't look the same on both lights (i know they should be different due to perspective but this has more issues than just perspective), the reflections on the side windows are confusing and the front windshield we see stuff that isnt in the BG...one last thing, i think you should've kept the wholes and number plate of the bumper as they were on donor, now the font looks too plain!
A full rebrush is very difficult and takes a lot of time to master so dont give up! This was a good attempt at brushing! I'll wait with a point and see what others might have to say about it
