How to change my ps3 NAT Type?

I have a Dlink DI-524 router and have opened the following ports (TCP: 80, 443, 5223 UDP: 5223, 3478, 3479, 3658) but it did not seem to help. I am currently getting a NAT type 3 and need to change it to 2. I have followed several tutorials on how to do this and none seem to help. Does anyone know how to do this?