If you have all the top mounts bits great its easy, but if you don't you'll need quite a few bits. Brackets, top mount, y pipe, dump valve adapter or recirc + piping. Then theres the cut out in the bumper and holes in that allowed the fmic pipes through. Maybe it's just me? Seems a lot of hassle to return to stock, when if you don't like the car that much, sell it and get one more to your liking.
But then I can't be arsed with all the crawling around under the car these days. Which is why mines stock :D