Audi RS6 AWD variant of the Boxster S gearbox. You'd have to lockup the center diff section, essentially making it a Boxster 6 speed transmission, before you'd be able to use it in a ME-RWD fashion.
I've never been inside one of those RS6 boxes yet, so I can't commnet on any other internal changes from the 2WD six speed version found in the Porsche's.