I have found that I generally get better mileage on country roads at 40-55 MPH than on the freeway running 65, as many on here will likely agree. Microsquirt might have helped some, but I would add some caution to your optimism about a 10% improvement. Most of that was probably from tire pressure and the change in your driving route.
Good luck getting it tuned up for even better mileage, though. I have always wanted to be able to play around with fuel and ignition maps on all of my cars. It seems they're always set from the factory to run safely on the worst garbage fuel in the world, so tuning to the good gas in your area should give you some improvement in performance and efficiency.
__________________
|