Another good place to check is the tdi forum. There is an entire section devoted to biodiesel. There's a lot of good info there that might be helpful. I recall there is one guy that ran WVO for something like 140,000 miles, and ultimately quit it. He put up a really good post that walked through all the mods he made to his car, etc. Anyway, might be worth a look, since VW has been bringing diesels over here for quite a while (as you know), and thus there is quite a rabid fanbase at that site.
Edit: Found the article I mentioned:
http://forums.tdiclub.com/showthread.php?t=315809