Unpack initramfs.cpio.gz (boot.img) from MTK6589 phone? I can't find a proper tool to unpack boot.img from GravityMod2.

both unmkbootimg and split_bootimg.pl are able to extract same fileset (kernel, 4280320 bytes and ramdisk, 633284 bytes). I think the files are damaged (taken from wrong offsets?) - can't even find gzip/cpio signatures in ramdisk image!

Is there another specific tool to unpack Android 4.2.x boot.img, or MTK-specific tool maybe?
I also had problem extracting initramfs.cpio.gz , until I opened this file in editor and seen first 3 ascii letters  (the header) in my case it was "LZO" , so I found proper soft to decompress 
"lzop -x " you can find it probably in every linux, for example knoppix has it

maybe you will notice other header in your file , so you will need to google it or have a good guess

good luck