Default [Q] Trying to install KK OTA - stock, rooted

Moved this question from here:

I'm currently stock, rooted, S-OFF, and TWRP recovery. I'm flashed to 3.06.651.6 firmware.
I still get the OTA notifications, and my goal is to install the latest OTA update (without RUU) so that I can preserve data. I've created a TWRP backup, but that's the extent of it.

Any help is appreciated.

Other background - I reverted back to 3.06.651.6 after flashing firmware because I could not boot normally after that or did not know how.
My bootloader says Tampered, relocked