Here is a link you'll find interesting:
http://e90post.com/forums/showthread.php?t=39270
It is very long, so cliff notes: It is an H8 bulb, 35W. If you put in an H11 (55W) you will throw an error code (afaik). The install is very easy:
1) Turn your wheels all the way to one side
2) Remove 4 hex bolts inside wheel well (and one under the car) (locations shows here:
http://www.e90post.com/forums/showpo...5&postcount=67)
3) Pull back wheel well plastic
4) Unclip wire to fog bulb
5) Turn fog bulb clockwise to remove
6) Replace.
Commonly used bulbs = MTEC Super White or Cosmos Blue, GP Thunder (8500k), Hoen Xenon Match.
Note; the angel eye bulb is also 35W H8, so any of these will work for that too. The cornering light is H3 (55W). Both the cornering and angel bulb are located in the same place; seen in the first post in the link above.
Here are pics of all the above bulbs installed as angel eyes (
http://www.e90post.com/forums/showthread.php?t=45408). Here is my car with GP thunders as fogs:
Inside:
Outside:
I tried MTEC super white, cosmos blue, and GP thunder as fogs and prefered the MTEC super whites since they most closely match the Xenons.