Tutorial: Exhaust
Adding an exhaust to the back of your virtual car need not be exhausting.... boom boom.
Difficulty - ***
A small pee-shooter like this? You iz no way gonna luk da bomb in maccy's iz u m8?  
Find a suitable donor exhaust. Maybe try looking on www.carandmodel.com, or have a good search on google.

Use the lasso tool - select, then copy and paste the exhausts onto the car they are to be fitted to.

Hit Ctrl+T and use the grab handles to flip, skew or change the shape of it to fit in with the car. Hit enter once you're happy with it. Then place it where you want it to be using the Move tool (V).  

Use the lasso tool to select and delete (delete key) the bits that you don't want... Ensure you leave a bit of the original bumper gap from the donor exhaust.. this looks like a cut out in the bumper then ;)  
If you fancy making it look more real.. you can add some depth to the cut out. Make a selection like the one on the left.  
Select a dark shade of the car colour, in this case a darker greeny/blue, and, using the airbrush tool, make a small dot of colour, like on the left..

Then hit Ctrl+D to deselect.

Complete.. Really needs a bodykit now...