Are you folks sure that you need to extract the boot.img to flash a kernel with 4EXT (S-on)?
4EXT asks if you are S-on when you first use it, which turns on the "S-ON 4EXT SmartFlash" option in settings.
I flashed the zip file, and the recovery log sure looks like it worked fine:
Code:
-- Installing: /sdcard/_Roms/Mobster Power Kernel v1.0.zip
Finding update package...
I:Update location: /sdcard/_Roms/Mobster Power Kernel v1.0.zip
Opening update package...
Installing update...
Installing Sense 3.6 Power Kernel...minzip: Extracted file "/system/etc/init.qcom.post_boot.sh"
Done...
script result was [Done...]
Install from sdcard complete.
4EXT Recovery Control finished..
Cancel reboot?
reboot in: 5
reboot in: 4
reboot in: 3
reboot in: 2
reboot in: 1
reboot in: 0
A pending update to your boot partition
has been detected.
Your rom will reboot once to finish the process.
A backup of your previous boot partition
has been saved at: /sdcard/4ext/boot_backup