Just a very late follow through on this topic: manifold nuts, and their R&R. I have replaced the original 11 mm ones w/ special 10 mm flange nuts, available through AirCooled and other VW parts shops. Work fine. Also, the trick here seems to be the use of what are known as "wobbly" extensions for your socket wrench. I have had these for some time, and they are pretty damn cool. Sort of like a universal joint but nothing more than a rounded shape to the end of the extension. Allows some slop in the angle between extension and wrench, and socket, and this is just the ticket to reach these nuts. They should be in every tool box.