Alright, so i think i got it working now. I did something different though than any method in this thread.
I fully restored my sprint 4S through itunes on 5.1.1
Installed cydia through absinthe
Inserted white reset sim and gevey and selected the sprint network
*Then, rather than deleting the entire carrier bundle, i opened it and open the iphone folder, which brought me to a TON of various carriers. I then deleted the Sprint_US and Sprint_OTA Folders, as well as the 310VZW folder the Zepplin_US folder and the Verizon_OTA Folder.
After that i installed furious mod and the corresponding CDMA package
Then i installed the backspace repo, along with the commcenter patch
then i powered the phone off and installed the gevey/ATT SIM and rebooted
Got the gevey message, wrote down the code and accepted. then i went directly to furious mod app and put the code in
I could make and receive calls fine, but my SMS texts werent going through. I remembered reading about that iglive repo and the network package, so i installed that and rebooted. It prompted me like 10 times that the gevey unlocked it and i accepted, and was never kicked out to the activation screen. Then finally the AT&T popped up and the 4G logo and immediatley received all the texts i had missed while it ras rebooting. I then proceeded to text everyone back with no problems.
I think this method will work if the Sprint or Verizon phone you are using is still activated with a sprint account. The phone i bought was on a delinquent account, and was still linked to it and i think that's what my problem was. Deleting the specific sprint carrier bundles along with the other US CDMA bundles freed up the PRL (Preferred Roaming List) allowing it to be used on the GSM network.
let me know if anyone needs help. Here is the link to the bundles i deleted specifically, and i added a few extra in that i deleted. It's hard to understand but it has worked flawlessly for me. I rebooted a few times and everything is still working great.
http://forum.gsmhosting.com/vbb/archive/t-1480321.html