I too am considering adding a Rear Air Dam and Side Skirts. After market (AM) of course. Now the shops I have gone to for installation so far are not inclined to install AM because they're saying that fit is a big problem. I am not yet deterred by all this! My immediate concern is buying from an AM distributor who delivers good quality stuff. I have checked Roaddynamics, eBay's Auto Shop, AutoTruckToys and DealershipsDesigns. However, what they have doesn't really tell me much about quality/fit.