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Welcome to the site and congratulations on your mileage improvement. You will find many mpg improvement by slowing down yet even further, to say 60 mph ( If the roads are favorable i try for 55 mph) you could save 5 more mpg, pump up your tires to max sidewall pressure and you will see that 5 mpg gain for sure.
If you were to start coasting on hills and changing gears earlier, keep your rpm lower before changing gears(shift 500 rpm's lower then you are shifting at now) And you will improve on it yet again(to be determined by your real life gains).
Your car has a mess of torque to propel you with, I suspect your tunes changed the fuel map to give your car more torque down low in the rpm's where it is more beneficial to the economy. About any tuning software can offer that if that's what a person wants.