I didn't do the differential equations to calculate this exactly, but using approximations and assuming atm pressure drops by 50% every 18,000 feet (meteorological estimate), and using an altitude difference of 4000 feet for my tuning location and the pass...ambient pressure should have dropped by about 10%. This is offset slightly by cooler temperatures at higher elevation. Using the ideal gas law to approximate the volume of air drawn through the intake and a temperature of 40F(pass) vs 85F (valley- summer tune) the amount of air fed to the cylinders differs by about 2%. In other words if my valley tune is 14.7 AFR, the pass would be aobut 14.4 AFR. Does that seem lean enough to melt a piston?
