From Artem - 5/30/11
"First off, the car you're driving is pretty much maxed out, as far as fuel economy is concerned (Lets not count the fact that an auto manufacturer will detune an engine to produce worse gas mileage, while still better then the previous model year, because lets face it, if they give you the best they can do today, it will be hard for them to beat that tomorrow when the next model is introduced - but that's a whole other subject better left for tomorrow's conversation)"
I saw a segment on a show a few years ago, no idea what show it was, about just this. A company in California does re-programming on your car's computer to allow the vehicle to work to its potential, instead of functioning at the everyday mediocre performance level that is passed off as top of the line. I haven't heard anythging about anyone doing this since. I imagine that it still goes on, however. There is definitely a market for it.