How do I fix my NAT type?

I have tried all of the conventional ideas that are easily researched. My NAT type is set to Open, I have UPnP enabled, and SIP ALG is disabled. Amazingly enough, my NAT type still registers as Strict on my computer and my Xbox 360. This is probably a one of a kind problem, hopefully not. Any advice will help. Even if it brings it to a Moderate NAT type.