Sure there are limits to what you can do by adjusting the engine/computer parameters, but for everything there is also a trade off. Americans are demanding consumers when it comes to cars. (For most other things they'll buy just about ANY Chinese CRAP out there.). You can gain a lot of MPG's by de-tuning an engine, but you soon hit the point where the vehicle is not 'fast' enough and suddenly 90% of your potential consumers vanish. Even as synical as I am, I'm amazed by the number of people who fully believe they'll DIE if they can't hit 0-60 in five seconds flat. So while there is plenty of MPG to gain by wimpifying the engine, they'll still have to look for other solutions if they want to be able to actually SELL the thing.There has to be a limit to how much you can accomplish by adjusting the computer. Otherwise, we would have 40mpg SUV's on the road. My bet is that Elio is already squeezing about as much mpg out of the engine as they can, and the rest of it has to be figuring out ways of reducing drag, such as the fenders from the P3 to the P4.
(And now follows a hundred people telling me they really WOULD die if not for having lots of power.....)