I did the headlite flasher version of the EV mod. Instructions are at
http://www.priuschat.com/forums/kb.php?mode=article&k=5.
It is a software thing. It's in every 2004-05 Prius, with the Japan and European models getting a button to invoke it. The battery pack is still well protected in that if the charge level drops below 3 bars the gas engine kicks on. If the engine is not warm (catalytic converter for low emissions), it will not engage EV mode (just beeps 3 times at ya!). If you over accelerate (too fast or up hill, or past 34
MPH) the gas engine kicks on to help. It's pretty cool though for parking lots or just moving the car outa the driveway/garage. I see no problem using it under limited circumstances since those overseas get to use it. I haven't seen 70 MPG yet and the manual does warn that excessive use might LOWER MPG, but I have been able to eek out 1-2 MPG using it selectively. Nothing is for free as far as energy goes in the Prius. If u use the electric, the gas eventually has to be used to charge it back up! Drive fun, drive clean, drive Prius.
'04 Seaside Pearl #7. Fumoto oil drain, mudflaps, rear bumper scuff protector & rear warn system, compass mirror, EV mode button, 8" subwoofer in right rear cubby & 6" subs under seats, power lumbar in the front seats, Coastaletech hitch w/ Aspen bike/snowboard rack. iPod2car, 2 amps, Alpine component speakers, and DVD video, solid 47 MPG @ 70000 miles.