The X3 doesn't display the absolute pressure as boost. What you're seeing is a calculation of Manifold Absolute Pressure (MAP) minus the indicated barometric pressure. Since barometric pressure is higher at sea level you will have lower calculated boost pressure displayed by the X3 computer at sea level and higher calculated boost pressure at altitude. Also, barometric pressure naturally fluctuates so your boost pressure is going to change day to day, lower on sunny days and higher on cloudy days. The fluctuations should be relatively low but could add up at lower elevations. Also, once you get over 24PSI (I think), the computer no longer accurately displays calculated boost.Cascade wouldn’t the air be denser at sea level so for every turn of the turbo wheel would get more air vs say 3000’ above Sea level? It’s like the pump would have 14.7 psi at the inlet rather than say 13 psi at the inlet. I’m typically at 500-1000 ft above sea level. I could reload the stock tune and compare the numbers.