With this tool you can edit gamesaves that are not yours.
How to use :
1. Open the downloaded game save with the Xbox 360 Save Editor .
2. Open Xbox 360 Save Editor again with your game save from the same game .
3. Replace the Profile id & Device id from the downloaded game save with the Profile id & Device id from your game save .
4. After that check the Local sign box & press Resign Save .
5. Make a back-up of your own game save. Then replace your game save with the downloaded one on the usb flash drive.
6. Start up the game and it should read the downloaded game save . Enjoy .