I have done the same thing with my 08 tundra when i was monitoring real time fuel economy via the OBD2 port/ software application... problem is you get focused your current "reading" and not on the road. Not fun for you, or anyone around you...; )Played with that technique of getting off the throttle and feathering it to just stay in 8th. Fuel mileage does go way up. My patience and comfort level goes to nothing.
Can't do that for long. It will drive you nuts. Hammer down..