Shatoshi has it nailed. Get a plate for each side or something to keep the screws all organized. I removed my bumper to install my TRD
rear valence. There are marks on the inside to drill the holes for the valence. While I wasn't crazy about drilling my bumper I figured, I won't be getting rid of my kit for a looooong time. And if I'm going to do it, I might as well do it right. One thing to watch for when you screw the valence on, it's kinda hard to get it the perfect "tightness" for the screws. I think I did mine a little tight and the "shelf" part that sits right under the black piece on the stock bumper is sitting a bit off the "shelf" instead of resting on it. So watch for that.