If you need to run higher, you might try dabbling with this addon: http://www.itsmods.com/forum/Thread-Rel ... addon.html
. Bear in mind, though, that this will likely break with new game releases, so you'll need to keep it up to date. We also do not know if it is legal.
The addon that John is mentioning does indeed work with the latest version of MW3. I would stay away from the plugins, as those tend to be slower to update.
If you do decide to run that addon, which I suggest you do. Be sure to set this in your sv_confg file.
//Disable the CPU/Bandwidth check [0-1]
I have a fair amount of experience with this addon, so if you have any questions let me know.