LED's in courtesy lights etc.
All in Japanese language on the E34 board in Japan. Example:
http://dd.jpn.org/BMW_HP/20050423/index.shtml

There is a lot in this archive on mods and repairs with a lot of good pics.
Maybe the mods have a look thru it and can divide it up into the sections, if they want.
For translation Japanese-English I suggest a link to altavista.babelfish
http://dd.jpn.org/BMW_HP/index.html

Have fun and work hard