Here is a guide who let's you to mod the Gears of War game
Needed -A Hex editor (I’ll be using Hex Workshop)
How to In wx360, open your GoW image and open the WarGame folder. Right click the Xbox360TOC.txt file and extract it to your desktop.
Now navigate to the WarGameConfigXenonCooked folder and extract the Coalesced.ini file to your desktop.
Open Coalesced.ini with notepad. Now the modding begins! We will be doing a very simple mod by changing the minimum players in a game from 2 to 1. This will allow you to explore maps by yourself. Find everything regarding minplayers=2. There should be two of them.
Now open the same file in your Hex editor. Search for minplayers=2 in the ACSI section. Change the 2 to a 1 for both of them.
We now need to balance the file out. As we have changed two 2’s to a 1; we need to change two 1’s to a 2. So you will need to find a value with a 1 in it that has 2 references, such as EndOfGameDelay=15.
So in the ACSI section, search for EndOfGameDelay=15 and change both references to EndOfGameDelay=25 like you did with minplayers.
Save the file and exit. Open the file in winMD5 and get the MD5 hash for the file.
Now open Xbox360TOC.txt in your text editor and on the third line down you should see: dcea2fa62810a22988798c77846bc2da is the original hash for the Coalesced.ini. So we need to change this to the new hash.
Congratulations, you have now successfully modded the minimum players value and balanced it out! Now you have to inject the new files into your ISO. So fire up ISO Injector v1.1 and open your image. Press Gears of War on the left and select Coalesced. Press Select File and find your modded version of the file. Now select Xbox360TOC and find the modded version of that file.
Make sure both the selections have ticked boxes and click Inject Checked.
Once the files are injected, burn the image to a disk using your preferred burning application like you would with any other Xbox 360 game and try it out! This method can be adapted to edit different values in the Coalesced.ini file, just as long as you remember to balance it out.