The speed can be caused by the other computers on the network with the Xbox. For example if you have say 5 computers on one single network with one internet connection there will be a difference in speed because those other machines are taking bandwith from the same place. If the ports are all open and everything connects where it needs to go there may be a wireless interference issue as well. Wireless routers like ours use 2.4Ghz frequency range and a lot of cordless phones do as well. You can try to set a channel in the router to somewhat calm that interference. If you log into the router just as you did when opening the ports and go to wireless config and then basic 11G you will wee under the ssid a wireless channel dropdown menu. Select channel 1, 6, or 11. Those are the strongest channels with no overlap in frequency.