[Q] NK2 to NCG?

[gatorhater73]

Having a problem... I have an S5 Dev Edition for VZW and I'm having radio problems. I had a rescue .tar that would bring me back to stock, rooted NCG, which was the only ROM i was able to get a cellular signal. Since upgrading to NK2 stock firmware (aboot.mbn deleted after i backed up my aboot) I have not been able to obtain a 4G signal (3G only) on ANY ROM. I want to downgrade BACK to my NCG rescue file and start over, but when I flash it now, it hangs at the Samsung splash screen. Is there something special I'm supposed to know (or do) in order to downgrade from NK2 to NCG? I'm ready to go ahead and flash a stock .tar (since I've got a backup of my unlocked aboot) but this is my last ditch effort to avoid that. PLEASE HELP!