1) Make sure you have busybox on your xbin folder.
2) Extract boot.img and ramdisk and place this lines on the bottom of init.rc
service sysinit /system/bin/logwrapper /system/xbin/busybox run-parts /system/etc/init.d disabled oneshot 3)Repack and you are done! You can now add any scripts you like to run at boot at /etc/init.d/ folder!