sure can, just plugs into cigarette lighter.

 

you can always add NOS stickers for HP and speed and the stick on louvers rather than a lower thermostat

 

The only thing that can give you big HP is putting a throttle body spacer in and then imaging you have a turbo system cause its whistling.

 

I have a 2007 4.7L QC and average 23 mpg on the highway at 65mph. My truck has some subtle mods, but nothing glaring. I did recently plug in a Superchips, but have not had time to get any mpg numbers. It all depends upon what you want to do, and how many $$$$$$ you want to spend.
[edit] Yes, I tend to have a light foot on the throttle. I also use the cruise control, unless I am going up steep hills. Then I cancel the cruise and hold my foot on the gas to maintain about 60 mph until I crest the hill. Makes a difference...

 

Oh that's no fun