Uh, just need 1 or 2 wrench types for the HE hex nuts, but if you can use (or afford) the other 10 sockets or wrenches in a set too, that's fine.
These work:
A properly bent 13mm distributor wrench (example):
Short square drive adapter with hex for wrench:
Related thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/687925-am-i-asking-trouble-playing-fire-trying-remove-exhaust-studs.html
Sherwood