More info about modifying a honda insight:
http://www.99mpg.com/Projectcars/mikesinsight/
The Prius uses a different form of technology compared to Honda's MIMA. A toyota can get higher MPG by converting to PHEV (plug in hybrid electric vehicle) which entails throwing a larger battery in back and making it so it can plug into the wall.
I researched this quite a bit a while ago but didn't follow through with the project. My MPG good enough
