Guys big credit to NGU for finding this Method, and this isn't my find its someone else's..

What you will need:
PSJailbreak/Groove
A PS3
Modern Warfare 2 (Disc or Back Up)
PS3 FTP Server by PS3News
Filezilla installed on nearby PC/Laptop on the SAME network

What this guide will help you to achieve:
How to edit and make a MW2 patch_mp.ff file
How to transfer your patch_mp.ff file to your PS3
How to play Modern Warfare 2 with your custom patch_mp.ff

Contents
- How to edit Modern Warfare 2 patch_mp.ff files
- What is a patch_mp.ff file?
- How to write your own mods
- How to get the patch_mp.ff onto your PS3


How to edit a patch_mp.ff file

What is a patch_mp.ff file?
As some of you may know, editing patch_mp.ff files for the PS3 is not possible at the moment. However, .ff files are not Sony files like SELF and SPRX files are. .ff files are made by Infinity Ward.
Here are the headers for each type of patch_mp.ff:
Xbox 360 Multiplayer Header: IWffs100
Xbox 360 Singleplayer Header: IWff0100
PS3 Header: IWffu100
A patch_mp.ff is a compressed file, just like .zip or .rar files. They store code that is applied to the game in .gsc files. GSC files are coded in C++, so having some experience in C++ will help enormously during coding. If you do not, it is not hard to understand the code anyway.
For Example:
if ( level.teamBased )
{
registerScoreInfo( "kill", 100 );
registerScoreInfo( "headshot", 100 );
registerScoreInfo( "assist", 20 );
registerScoreInfo( "suicide", 0 );
registerScoreInfo( "teamkill", 0 );
}
It is not hard to understand that this displays the amount of XP given to a player for different types of kill.
Now we understand what a patch_mp.ff file is, we can move onto editing them.


How to write your own mods
In order to edit a patch_mp.ff file, we need 2 things. One is an Xbox 360 patch_mp.ff file and a program many of you will have heard of called ffViewer (Download Here). Please have ffViewer on your Desktop before continuing.
Open up ffViewer, you should have the latest version. At the time of writing the latest version is v2.64. Go to Tools, Get patch_mp.ff TU6 and wait for it to open.
Now you have a plain patch_mp.ff file. If you arent confident that you will be able to edit the file well enough, just download GODLYM0DZ patch found here.
Now go through and edit the file. You may want to read this article on NGU for details on editing it. Be sure to fully understand it and how to use DVARS and how the GSC file works.
Once you have finished editing your file, you can continue.

How to get the patch_mp.ff onto your PS3
Turn on your PS3, with your jailbreak, and delete the Modern Warfare 2 patch in Game Data Utility. Then start up Modern Warfare 2, download the patch and then quit the game. Now start up the PS3 FTP Server. Go to Filezilla on your computer and enter your PS3s internal IP address (can be found in Network Settings on the XMB). Enter the username: FTPD12345 and no password. The port is 21. Now FileZilla will connect and you need to browse to the following directory:
/dev_hdd0/game/BLES00683/USRDIR/
You will see the patch_mp.ff file in there, you need to open that in a hex editor, and open your custom patch_mp.ff in a hex editor. You then have to copy and paste all the code from your custom patch into the patch on the PS3. Now that is done, save the file and FileZilla will ask if you want to re-upload to the server. Choose Yes.
Now turn off the PS3 and turn it back on (with jailbreak!) Finally, just start Modern Warfare 2 from the Disc and you will have whatever Mods you chose!

I will be adding downloads as soon as