Credits to Hot Uniicorn for his research!
Tutorial:
1.Extract Profile to desktop using Horizon
2.Open Profile in horizon, click "Content" tab, click the search box and search for "415608CB" click the 415608CB.gpd and click extract, extract that to your desktop
3.Open 415608CB.gpd in HxD (hex editor)
4.Click Ctrl + F Should get a search box like this:
5. Now you can search any of the following and mod them, I've gave some examples in brackets:
2F04 = BLACK OPS PRESTIGE (00 00 00 0F = 15th Prestige)
3004 = BLACK OPS LEVEL (00 00 00 32 = Level 50)
3104 = MODERN WARFARE 2 PRESTIGE (00 00 00 0A = 10th Prestige)
3204 = MODERN WARFARE 2 LEVEL (00 00 00 46 = Level 70)
3304 = WAW PRESTIGE (00 00 00 0A = 10th Prestige)
3404 = WAW LEVEL (00 00 00 3C = Level 60)
3504 = COD4 PRESTIGE (00 00 00 0A = 10th Prestige)
3604 = COD4 RANK (00 00 00 37 = Level 55)
^^ For example: search for 3104 then find the highlighted numbers, then 3 sets of zeros to the left of that you will see a number change that to "0A" that makes you 10th Prestige in MW2!
6.Click Save
7.Open up horizon
8.Open profile and Click Content tab and find 415608CB then right click, replace it with the modded GPD
9.Rehash Resign
DONE!
^^it should look like this when done!
*NOTE*
It sticks if you let your GPD sync to the server
ENJOY YOUR PRESTIGE EMBLEMS ON YOUR GAMERCARD
[TUT] How To Mod All The Game Ranks In Gamercard 
Linear Mode
