INJECT ONLY IN MAIN MENU. (WAIT 5 SECONDS PRIOR TO INJECTION)
For TeknoMW3, just join a server for it to auto-activate as with all versions.
For IW5M, on the "Connecting..." screen, press Shift+Enter within 5 seconds. Your name and GUID automatically resets to the original within 20 seconds. This does not occur with TeknoMW3. I have verified this is patched on IW5M. Do not complain if, in your ignorance, you use this and get banned.
And no, you cannot disable the name faker.
Just use Extreme Injector and inject to game process.