OK, i actually tried to remove mine then other night - it can be done if the bumper is removed but it looks as though it will take a bit of elbow (and fist) - there are a load of retaining clips between the diffuser and bumper (you'll know the ones!!) and as far as I am aware, YES, the S4 diffueser will go on. It's about £100 or thereabouts new from Audi and obvioulsy comes in a slightly different shape / mould as well as a slightly different colour. It's worth noting the S4 diffuser design is also used on all B7 A4 Cabs as well........