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I cant seem to find the OTA file for 1.54 anywhere but if you find the OTA zip all u need to do is copy it to internal storage and boot into recovery by turning the phone off then turn it on while holding volume down and then select recovery using volume buttons and putting power, after that its just select apply update from internal storage then your good to go. I couldnt find the 1.54 but if you do find it heres the 1.55 update http://d-h.st/AEv
So apparently 1.55 is the first update for the verizon htc m8 which is the device u have. The update does not include extreme power savings and it appears the only way you will get EPS on your device would be to root and flash a custom rom with the feature enabled. Before you go and download a rom though you need to make sure your in the right section. Go to this section http://forum.xda-developers.com/verizon-htc-one-m8 it is the verizon htc one m8 thread. In order to be 100% sure that you are on the verizon version of the m8 go to hboot by turning off the device and turn it on while pressing volume down and make sure it says something like M8_vzw on the very top of the white screen.