This is how you mod your gamerscore:

1)First you have to have a usb 1gb or more then put that into your xbox front or back dosnt mater.
2)go to system settings, memory, memory unit and then click configure then go to hard drive gamer profiles and click move to usb on the one you want to mod.

3)Once youve moved your profile over take your usb out and put it in your laptop or pc. Go to haddz gt editor and open usb click on your profile which should say EOOOO2... ect then click on that then click on FFFEE... ect then click on ooo1ooo.. ect then it should say (file)EOOOOO2... clcik on that and press ok.

4)Then it should say your gt. Click on the 2 in the top left corner and go down onto achivements and then a box should come up.

5)Now go to were it says current game and click on the drop down box and click on the game you want gamerscore from. You can either click unlock all games or you can do a achivement one by one to do that go to where it says unlock on line click on that then click on unlock OFFLINE the just update achivement just carry on doing that untill youve done then click on fix rehashes/resign and then click on save to profile.

6)After doing that take your usb out of your laptop and put it back into your xbox.

7)Go to system setting memory the go to meomory unit click on gamerprofiles and click on your profile and move back to your hard drive and sign back into your profile and you should have your gamerscor higher than you last had it.

If any problems send me a msg on xbox (BumWhiipZ x325)