I see, you're doing the US-version. Not so pretty in my eyes, but well. First of, some few reference pics (US and RoW models mixed):
I actually was about to write a bug list, but those are just way too much. Just have a look at the photos and compare them with your model, you'll find more differences than similaritys. On a side note, the 911 always had reverse lights and a plastic grille on the hood. Also, the rear window frame does not go up to the flat part of the roof. There is an air outlet between it.
The US models (your mesh is one) have wider rubber boxes on the rear bumper, the ugly sealed beam headlights and the front signals have doubled width.
I permitted you to use my wheels, but map and use them correctly please. You used the same wheel four times which is wrong, the rear wheels are wider and have different proportions than the front wheels, I modeled that.