I cant get my nat to open on the ps3?

I cant get my nat to open on my ps3, it is reading as nat type 2 on the ps3 settings. I have a linksys wrt160n router. I have tried evrything i could think of, opening/forwarding ports, dmz hosting, different videos for setting up the router. i even called activision to get the ports for modern warefare2, still nothing, playstanion doesnt seem to know why either. any help would be very much appreciated. thanks