同じ事言ってるやつが居た
http://forum.xda-developers.com/showthread.php?t=2527485

If you are unhappy/unsatisfied with the 4.4 factory image, you might have to reflash the 4.3 OTA or the 4.3 bootloader/radio to get WiFi working correctly when restoring an old backup.

Without doing so, you might experience long boot times at the "Google" logo and WiFi being disabled (which you can't turn on) when the OS finally loads