Hi mate ! Wrong section but i'll try to help you.
I read again your post, so, i guess you can simply flash an EMG4
^Try this before this :
I'll make it quick, and if you don't understand, i'll develop. Also, i apologize for my bad english.
1 ; Delete your EFS folder
2 ; Reboot in recovery, connect your mobile to the computer.
3 ; On your computer, start an ADB session and type, in the exact order the following commands :
mount -w -t ext4 /dev/block/mmcblk0p3 /efs
Once it's done, reboot your phone and check if your IMEI is back. If not, reflash an EMG4 modem and restart your smartphone.
Let me know how it's going, PM me if you want, or, you can add me on Skype ; Orath. (Don't forget the dot
Xperia Arc LT15i - 8Gb Unlocked Bootloader / ICS 4.0.4
iPhone 4S Black - 16Gb / iOS 6.1.2 JB
Samsung Galaxy S3 - 32Gb + 64Gb SD