EUREKA!!! I found a fix!!!!!! Happy Saturday everyone!!! I struggled with this same issue for about a week when I first rooted my S4. I'm a noob to the Android OS. YES! I've been and iOS'er since 2008! Got the new galaxy and was feeling naked, so I did some research on rooting, custom ROMS, etc... Just like you GameKiller would not work for me, it would say it needed root privilege and it would just crash. The past 48 hours I'd been trying to get unlimited $$$ on Galaxy On Fire 2 HD...and last night I finally did. I even got Freedom apk to work with this method.
I would like to share my experience also, and yes it is a success. But, I'd also like to let you know, I just started doing this. SO, listen carefully and pay attention to what you're doing. That's all I did. If I could figure this out in 24 hours. I'm sure a consistent Android user could do it with ease. But still, I'm in no way responsible for what another Android user does to their phone. So, whatever you do and whatever happens, it's at your own risk.
CHECK YOUR PHONE'S MODEL# TO MAKE SURE IT COINCIDES WITH THE CUSTOM ROM YOU'RE INSTALLING!!! The tutorial I'm doing is for the Samsung Galaxy S4 GT-19505 (Basically this is for the North American S4 with LTE). DON'T CONFUSE WITH GT-19500 (European Galaxy S4), it WILL BRICK YOUR PHONE. So, if in doubt, go to Settings>More>About device and check your model# and whatever else you might want to.
Galaxy S4 GT-I9505
Rooted & Running XWUBMGA V1.4 WanamLite ROM via ADAM1.5 Kernel.
Info Link: WanamLite XXUBMGA V1.4 Android JB 4.2.2 Clean & Stable -
What you'll need:
1. A rooted Samsung Galaxy S4 GT-19505, running (STOCK) JellyBean 4.2.2.
2. Custom ROM .zip File on external SDcard download files GT-I9505_WanamLite | Romcook.com
3. GameKiller V2.61 APK Zippyshare.com - Game Killer v2.61.apk
4. Copy Custom ROM TO external SDcard
5. A CWM recovery (I recommend Rom Manager. VEEEERY QUICK & SIMPLE!)
6. Backup your current ROM
7. Install custom ROM .zip file from external SDcard
8. Reboot (Don?t use the Root option from recovery (you don?t need it)
9. Now, install Game Killer V.2.61