You will need to backup of your nvram from your phone. How to do it check my first blog post - Method 1.
- download this file: http://d-h.st/LPDX and unzip it on your computer,
- run the SP Flash tool, and than press the ctrl+alt+v keys on keyboard to get advanced mode
- select scatter.txt from imei folder
- click on "Window" and then on "Write memory
- copy your backed up of IMEI file nvram.bin, previously created with MtkDroidTools and rename it to nvram.emmc.bin - don't change the file extension *.bin
this is collected and rewrited guide from different sources on internet. thanks to xdaforum users, also thanks to user with nick smokerman.