Your on CM11, go to its recovery, do a nandroid for backup of your current ROM just in case, wipe data and flash the existenz ROM (no need to flash the boot.img separately if its already inside the existenz ROM.zip).
Tapatalked from my Xperia P
Recovery's started flashing kernels a long time ago lol your previous device probably didn't support it!
Sent from my C5303 using XDA Free mobile app
Hehehe, true, I myself had the x8 and Arc last time and you must fastboot the boot.img everytime. But "hot" booting works last time, which I believe doesn't now.
Tapatalked from my Xperia SP
ah yea :S mine was neo v from the same 2011 xperia line as your arc xD