Did you manage to get it installed? I ordered the unpainted version from Concept Z. Do you have a copy of the instructions they gave you? All I got was the diffuser with the 3M adhesion promoter but no screws. The instruction say nothing of removing any part of the OEM bumper, and do not mention using screws, however they list a drill with phllips head screwdriver as a necessary piece of equipment, so I'm a little confused.
I'm taking it to a local body shop to get it painted and installed next week so I hope I'm not missing anything.