No mods to do except to cut a " V" notch in the lip so the lip can move back on each side to conform to the shape of the XF. Basically, there is a bottom piece on the lip that is about 18-20 inches long, find the center, cut the "V" , about an inch or so on either side you will put a self tap black body screw. Besure to angle the screws so they go into the bottom of the bumper and not the front of the bumper. You don't want them to show if you remove the lip later. I used black license plate screws. You will want to place another screw about an 1-2 inches from each end of that center piece. That will give you 4 screws in that flat piece of the lip. Now you will need to pull the ends around the body. I lined mine up to the body indention( see pics in previous post) that ends at the wheel well. Pay attention to the angle of the ends of the lip, I made mine square to the ground and installed two more screws on each side. Remove the whole lip and clean with 91% alcohol, also clean the bumper with the alcohol. I would clean it several times with fresh cloth and alcohol. Put at least three short pieces ( 6inches long) on each side of the lip, at the top edge ( do not remove red backing yet) check the fit as you go, once you have the fit you want remove the backing from the tape closest to the center of the lip. Push the lip to the bumper making sure to lineup the body line. Remove the next piece of backing and line up the body line, push lip to bumper, now remove the last piece of red backing. This piece of the 3M tape probably wraps around the turn of the bumper to the wheel well. Repeat the process on the other side. Should at this point be finished or close to it. Hope this helps you do the job. Read several times to make sure it makes sense to you. If you have any questions, I'll be glad to help if I can.