My efforts below:
OEM S4 B7 Grille

So the OEM Grille has hollow slats running Vertically which on every other 'S' range Audi I have seen are Chrome.
Chrome Effect Styling Tape 7mm - Self Adhesive (Lidl's £9.99)
I found some self adhesive chrome effect strips in Lidl's. It comes on a fairly big roll. As the strips are 7mm wide and the Grille has a hole barely 6mm wide, I had to trim some off (which was a bugger to do as I only needed about 1mm off)

It needs to be a really tight fit so it wedges in the gap as there is nothing really for it to attach to. The longer of the strips fitted in really easily but the smaller ones in the middle of the grille had to be superglued.



Pictures