Unhappy [Q] Help with generic EFS/IMEI S4-i9500

Hello, I was about to take my phone to a service center for check an weird noise, but since I was using CM11 with chinese modem, I decided to flash stock rom.
I'm on the old bootloader, I flashed I9500ZTOBMG1 but when I try to make a call it shows "not registered in network". I checked my imei with *#06# and it shows a generic IMEI starting with 0049...
I have already tried to reflash stock rom via odin, reflash stock modem via odin, restore to last CM backup, but problem still.
I DO have a EFS backup, it's a .tar and a .tar2.gz inside a folder called EFSProBackup, but I don't know how to use it or even how to restore my IMEI. I had already this problem before, but I don't know what I did to resolve. Can someone help me?

Problem solved: I flashed again the chinese modem via cwm after flashing a custom rom, I don't know why, but my imei is back again and working, But I still don't know how to have stock rom working....