You can tell if its rep or not if the cf part is a plate seperate from the paint. A real mugen spoiler has one plate and its entirely cf. some people paint the edge of the cf plate to make it look like that pic posted. Unless your there to touch it and notice if its 2 seperate peices theres no other way to tell of its rep or not if he painted it that way.
The sticker is a mugen sticker that comes with the authentic mugen wing. They make those stickers in reps but you can tell the diff