I agree with the TURBO... !! Think something like a STS (rear mount) Fuel economy will improve providing the operater keeps their foot out of it.. Benefits the people living at higher altitude (Colorado etc) will not experiance a power loss as with N/A vehicles.. Another benefit is better if there Elio will provide a method for towing a trailer, the turbo will "pull" better..
The cool thing is technology for fuel injection and turbo's have come a long way in the past 10 years so this option is really a "do-able" situation. The key thing is the ECU will it be open or allow access etc. This could also be as simple as changing a chip out or a piggy back type of system.. This could be so easy it could be a factory option...