How to Mod Your Forza Motorsport 4 Level and Credits
Move your ForzaProfile from your HDD to a USB on your Xbox 360.
Plug in your USB to a Computer, and run Horizon. (Download Horizon here: [ Register or Signin to view external links. ]
The device explorer should pop up, and look like this:
Open up the Games folder, then Forza Motorsport 4, the click on your save that you moved in Step 1 and finally click the Mod button.
The editor will open up and look like this:
Change the values to whatever you wish.
Click Save and then close.
Remove your USB from your computer, and plug it back into your Xbox 360.
Start Forza 4, and check out your stats! Enjoy!
(video coming soon.)