I’m sorry, Xbox has released many updates since that post.  I haven’t gone back to it to see if there are other ports that need to be opened.  I’ve read from people’s comments that placing the Xbox in DMZ using your router gives full access to it from the Internet, so you could see if that’s a possibility for you.  I would recommend only doing that temporarily, though.  Seems like it might be a security risk if left there permanently.