i just got a 99 A6. does anyone know if these came stock with hid headlights? i assume they did because mine look like they are (they flicker on then get way brighter in a split second). but im not sure because i noticed while i was out just now that the drivers side is not nearly as bright. and it looks kinda regular white (like a silver star) while the passanger side is bright bluish and projects much farther down the road. it actually dwarfs the dimmer side. does anyone know a little about hid? if so, does the one bulb just need replacing and are they more expensive then regular bulbs?
if not, is it possible that it is something more serious wrong with the drivers side?
also while we are here... what is the difference (if any) between xenon and halogen?

 

it is better to replace both bulbs at once... IIRC the xenon headlights dont have dimples around the main projector.

also... the xenons have the ballasts attached under the headlight housing.. look for this little box (and that red plug going in to your lamp):