I had someone email me asking what mods were in place on the Firefly for the Green Grand Prix. Here they are, plus driving notes:
Aerodynamics: - additional grille block (in the hood/bumper gap; see Wonderboy's pic, above)
- regular partial grille block (home made "bra")
- headlight gaps sealed
- one (1) front wheel skirt 
- smooth wheel covers
- radio antenna delete
- passenger mirror delete (internal convex mirror in its place)
- driver's mirror folded back on highway portion of route
- rear wheel skirts (2!)
- Kammback
- washed & waxed before the event (just kidding! NOT an aero benefit!)
Drivetrain: - tires around 50 psi (didn't actually check before the event, embarrassed to say)
- 5w20 synthetic engine oil
- GM Synchromesh semi-synth transaxle oil
- Metro XFi camshaft
- transmission with taller final drive ratio
Electrical - plenty of use of the shifter-mounted ignition kill switch (for P&G, engine off coasting)
- alternator electrically switched off past the half-way mark
- daytime running lights used selectively depending on perceived risks (installed an "off" switch)
- I listened to the radio during the highway portions of the drive though
Instrumentation: - ScanGauge 2, monitoring: instant MPG; tank MPG; average speed (time limit); open/closed loop; voltage (after switching off the alternator); elapsed time (watch)
Driving techniques: - Pulse & glide, monitoring SG to keep engine in closed loop during pulses
- Light timing & traffic timing in urban areas to avoid stops & minimize slowdowns - driving without brakes
- Moving to the extreme right of my highway lane ("ridge riding") or part way onto the paved shoulder to facilitate/encourage passing by faster traffic (there wasn't a lot).
- Pushing the car (part way) to the start; at the mandatory rest stop in Geneva; in the gas station for the post-competition fill
- and more than a few other from our 100+ eco-driving / hypermiling tips
I think that's everything...