Jay correct me if I'm wrong, but you don't have an S4 do you? Normal A4's have a two piece bumper, whereas it's a one piece unit on the S4.
My bumper and the S4 have the same set up, the only difference is the shape of the diffuser / valance - I was under the car last night and he's spot on, you have to remove the bumper (unfortunately!) - it's a shame as I wanted to take it off and spray in black but I will have to come up with a plan B now!