Posting this for a friend. He has a pair of BRAND NEW Bailey Motorsport DV30 Diverter Valve's he purchased for his S4 that he ended up not using. Check out the ebay links below. As of yet I havnt picked up an S4 so I thought I'd let you guys know. He's also willing to sell em separately for single valve applications...

Audi S4 2.7T (2 valves)
Audi A6 2.7T (2 valves)
Audi Allroad 2.7T (2 valves)
Audi A4 1.8T
Volkswagon Passat 1.8T
Volkswagon Mk4 Golf
Volkswagon Jetta 1.8T
Volkswagon GTi 1.8T
Porsche 996 911 Twin Turbo (2 valves)

ebay link

2nd ebay link