BASE:
http://auto.aggress.ru/images/7/CRX/Honda_CRX_Si_1988_30wvert.jpg

CHOP:


C+C Welcome

first of all, post a big picture, as big as base, and use feathering feature in lasso/pen tool when making selections so egdes will be smooth.

in this size i can't see if You even tried to do some reflections or are these jpeg artefacts

The size of the chop is the same size as the original background picture

žDont think that im to hard on u this is just my opinion.
- looks unfinished
- it is toony (not realistic)
- also in some places color is oversaturated
and just like cudak said try to use pen tool for selection u have tutorial for pen tool here
http://www.autemo.com/forums/?t=6960
and u have a lot more than just a pen tool tutorial

Cheers I appreciate the critism