what headlight bulb can i replace my hid bulb with in my b5 s4. sylvania.com says i need a d2s bulb? i want to put some 8000k bulbs in there but no place i look sells the d2s, is this just sylvania's code for an h7 or something?

 

You need d2s. This is the OEM HID bulb. Phillips also makes thesebulbs.
Check E-Bay.
Don't go above 6000K .

 

Oem is 4300k philips, the philips 6000k are $200 on ebay shipped if you want to swap in color. Try to avoid generic brand bulbs, i've heard of some people getting some really short life out of them.