I was doing exact thing as you. Got told how eventually. We missed out that no one actually tells us to backup the game lol. Thats because MW2 can not be backed up and run successfully(just a stuborn game lol). All you have to do is, run mw2(using disc) and install the 1.11 patch. Then start up the ftp server on ps3. Browse to dev_hdd0/game/bles00683/usrdir and delete the patch_mp.ff. Then put a modded patch_mp.ff in its place. Exit and run the game from disc