You can get the stock airbox that's down behind the bumper out by simply removing your passenger side wheel and undoing a few of the screw/clips holding the black plastic liner in your wheel well. Fold the liner back and badda bing you pull it right out whithout having to take the whole friggin bumper off.

Either way will work though but my way takes about five minutes. You can try doing it wihtout taking the wheel off too by just turning the wheel all the way out... it's a little harder with the wheel on though but can be done.