I'm gonna run The Tomb of Horrors for level 15-17 chars...

[Land Outcast]

http://www.thealexandrian.net/creations/creations.html

The conversion on that page is not quite what you're looking for, as it's a more thorough conversion than the WotC 3.5 version, but it is balanced for 15th level play. I've run it as such and had a fairly good experience.

Thanks for the link