Tutorial: Adding BMW Z3 style wing vents
A pretty unique styling modification, that, once practiced, is pretty easy to master.
       
 Z3 style vents
 
Difficulty - ***
For this tutorial, I'm using a Ford Focus as the test bed, I'm gonna pop the vent on it just above the side indicator..  
First you need to find a suitable donor image. There are a few after market ones about, so try looking for those on modified car pics. Just for you, I have got a little collection of them for you to use! Just right click them, and save to an area of your hard drive.  

Righty.. Copy and paste the required vent onto the car! And transform it, so it looks correct on the car.

The Transform option is accessed using Ctrl+T. It's a basic grab handle system (hold the shift key to skew it).

It SHOULD look like summit on the left! Just make sure it looks part of the car (same angle and perspective etc!)

 
Lower the opacity of the layer to about 50% (using the layers box (bottom right).

Then, use the eraser tool (E), and begin blending it into the bodywork. Select a suitable brush size for the application.

 
Increase the opacity back to 100%.

Now we can begin to colour code it. So, desaturate it

 
Then head for Image>Adjust>Variations.

In this case, I wanted a hell of alot of blue, so I added loads of blue.

 
Next you go to image>adjust>hue/saturation... and FINE TUNE the colour so it matches perfectly. In this case I needed to adjust the colour slightly and the intensity of the colour. This is done by sliding the adjustment bars.

Ok, once you've done this, adjust the opacity slightly to around 90% so it blends in nicer!

 

Complete! Looks sweet huh?!