Own a Sony Xperia Z ultra and want to unbrand it? Well consider using this XDA tool to obtain root as well. This firmware works on both unlocked and locked Xperia Z Ultra phones.
1. make sure to be on a rooted rom with Philz recovery
2. download the ROM on your External SD
3. reboot to Philz recovery
4. wipe (data, cache, dalvik/art cache) and format (cache, system, data)
5. flash rom
Here is its build.prop file which is said to improve Wi-Fi and 3G signal. You can replace it in Root/System with a file manager root setting RW-R–R—permissions.
I have the ROM installed on my Xperia Z Ultra and it is the most flawless ROM out there. I did remove loads of apps and firmware to suit my own usage and that was easy.