This tune is rock solid above 20 MPG for sure. It is repeatable. The first test trip was from Riggins, ID where I filled and the to Donnelly, ID then to Lewiston, ID. I netted 28.04 MPG. This last trip I've gone 425 miles on just a half tank of fuel.
You must have a final ratio to the ground close to 3.73 gears. I'm 3.69:1 ratio with the 245/75 R16 tires (30.5 inches) I'm running. Injectors are +150 HP DAP VCO Injectors popped at 320 bar. I'm running a slightly bigger turbo HX35/40 hybrid. Drive to speed limt but no rocket launching from stops. Take your time building speed up.
425 miles on just a half tank of fuel. Not many can do this...
Hand math on the first test run.