[Q] How to update a M8 with old software topic

I need to know this before i brick the device or something.

The device is running the 1.54.401.10 software (4.4.2).. I believe this is the oldest there is. It also has a unlocked bootloader, S-OFF and a CID of 111111... How can i update this phone to the 4.4.4 version? I've tried with the inbuilt OTA update, by searching for updates from the about -> software updates menu, but this does not find any updates, so i must find another way to update it.

Can you guys help?

Thanks!