Ok I guess my experience of older carberated gassers in the mountains and more modern fuel injected diesels left a void. I swear I have also read what I repeated but honestly I don't have anything other than those experiences to back it up. So I guess I stand corrected. Well fwiw my FI turbo charged & intercooled Buick Grand National was more sensitive to altitude than my diesel also.
I don't know why BTUs come to my head but more of this type of power detonation resistance not sure what the proper term is in diesel than in regular pump gasoline. They just always produce the same or more torque on less fuel.
As far as the EcoD I've had great luck with mine. Runs great tows well to the limits of the 1/2 ton platform. Responsive great on fuel quiet and smooth. The 8 speed is fantastic. Great gear spacing economy and keeping you in the powerband smooth and quick shifting. Basically only maintenance so far a light switch, wheel stud, tail light bulb, wiper blades and tires plus an alignment at 196k.