Do y'all really not know?  I can never tell with some of you guys.

Well, if you don't know, and since someone asked how to do it instead of if someone knows how to do it, I will tell you.

If you want to change your NAT type to Open just forward the ports for this game on your router.

www.portforward.com will tell you how.  Just look up the ports you need to forward for MW3 Wii.  Then look up your router and it will tell you how to do it.  I hear putting your router in DMZ mode works too but I never tried it.

If you want to change back to moderate, at least for me anyway, I Just simply turn the port forwarding off on my router.

Also, sometimes forwarding the ports will still keep your NAT type as moderate.  If that happens you probably did it wrong so double check your work.  If you double check your work and it's right, then try forwarding the ports while using a wired connection instead of wireless.  That's the route I went, though I didn't have to, but it is more stable.

lol ur wii's disk reader will explode like mine did

Yes, but without the "Red" color... Putting color is overrated.

Strict for the win

Oh I see.  Take the easy way out. Oh the shame!

Semper give that a shot.   Though the computer nerd side of me wants to try to make it work without any wire snipping....

I did some more reasearch into my situation.  I haven't confirmed but it looks like my problem is my modem.  Not my ISP.  My buddy who has the same service, but a different modem, has a NAT type of moderate.  His modem doesn't work with my router though.  Currently I either need to upgrade to a different setup (something I didn't know existed but is a sweet deal), or wait for the router firmware to catch up with these new modems if I want to achieve an open NAT again.  Either that or switch back and forth between my different speeds. Oh the joys of living out in the country.

So Beast your modem could be the problem as well.  You would have to do some digging to find out.  I was on the phone with my ISP for over an hour trying to get answers.  The rep of course didn't know anything but I did some pushing and got her on with their tech guru.  Between the 3 of us I got some answers. 

Well good news Beast.  Everyone told me that I was stuck on strict no matter what because of the modem I have chose.  They were wrong.  I figured out how to get mine to moderate and make it stay there.  There may be some hope for you at least.  I had to connect to my modem through my router and make a change to it.  I'm going to see if there is anything else I can do to get mine to go to Open. 

Oh, and the reason I say there is hope for you is everyone I asked told me I was SOL and stuck on strict.  They were wrong.  There's always a way.  Just have to find it.  I may not be able to do better than moderate but we'll see.