start the hack with full rights > start game > while in loading screen press the F9.. Stuff... or just press it while ingame.. that worked for me.. but still laggggg :$ Dont forgot to put those files (the hack) inside the mw3 folder that is inside the steam folder.
(download link got deleted, didnt know about the outside link.. the TS also posted an outside link inside the file so yeah.. i was just trying to help those who cant download..)
Here is a safe new download uploaded on mpgh itself, didnt know about the feature but anyway.. this is exact the same file, so no worries.