[One (M8) Q&A, Help & Troubleshooting] BerndM14:
Firstly: This is the wrong section for this thread, it should have been in the Q&A section.

Onwards:

Preparations and "tools" needed before attempting the conversion back.

Make sure to download the 1.54.401.5_W_Splash.zip firmware from this thread - Going back to Sense

Download the Bell Mobile nandroid backup from this thread - Stock Backup & OTA Collection There is only only Bell nandroid backup so the 1.55 will have to do. The stock recovery for Bell is also available in the first post.

Make sure to unzip and place the nandroid backup in the correct path on the SD card(If you have one) on your device. If the the path(TWRP) does not exist yet, just flash TWRP and create the path by making a backup of just the boot sector.

Change to SuperCID on your device(Ease of use if for no other reason). fastboot oem writecid 11111111 <<That is 8 1's.

Download latest TWRP from http://techerrata.com/browse/twrp2/m8

Place TWRP, Firmware(1.54.xxx.zip) inside adb/fastboot folder

I take it that that MID(0P6B16000) is the original MID for your device and that you never bothered to change the MID to Google's? If that is so then we have one more step completed.

Ok, your phone should still be in bootloader mode after the CID change, type - fastboot reboot-bootloader just to make sure the CID and everything reads properly.

Type: fastboot oem rebootRUU

Type: fastboot flash zip 1.54.401.5-W_Splash.zip <Important, the name needs to match the firmware name you downloaded EXACTLY!!!

After flashing the firmware you'll probably get an error 90, DO NOT reboot the phone, flash the firmware again with the same command fastboot flash zip 1.54.401.5-W_Splash.zip

After it finished and shows success reboot the device with command: fastboot reboot-bootloader

The firmware.zip already flashed a stock recovery for the device so boot into stock recovery - In bootloader select HBOOT then scroll down to recovery and select with Power button(Yes, I'm telling you everything you probably already know or should know).

You'll reach a screen with a phone in the middle, in the phone there'll be a triangle and an exclamation point. Press Volume Up and TAP the power button to enter into stock recovery menu(Should be blue text if I recall).

Scroll down to wipe/factory reset and select with power button. Scroll down to Yes to perform factory reset.

Reboot back into bootloader.

Flash TWRP recovery: fastboot flash recovery name_of_recovery.img - it'll be something like openrecovery-twrp-blah-blah.img <Make sure it has only 1 .img at the end and not 2 !!!

Enter TWRP recovery, go to Wipe and select factory reset.

Go back to TWRP recovery and select "Restore" and select the path/location where you placed your downloaded Bell nandroid.

Flash back stock recovery: fastboot flash recovery recovery.img

Clear cache: fastboot erase cache

You can now change CID to old Bell CID and do OTA's if you want.

After the converting is finished, in order to get back to stock fully, you'd might have to get rid of any flags that was triggered while "tampering" with the device.

[how to] remove your "tampered" banner

[how to] lock/unlock your bootloader without htcdev(s-off required)

After all is said and done you can then continue towards your bathroom/bedroom, stand in front of a mirror and ask yourself "Who the Hell pays $25 for Sunshine S-OFF just to give the phone back after a couple of days, in order to exchange it for a plastic Samsung?"