Inspiration for your mountains Y-axe painting - Look at this video
The BEST rally video you will ever see(No music, RAW sound) - YouTube
That is pikes peak 0-4000m
That ECU has 1 bar internally atmospheric pressure sensor mapped to correct ignition, fuel and boost on its way to the top (by the way +2 bar forced induction)
Such internally 1 bar atmospheric pressure sensor is standard in all professional aftermarket ECU EFI today for such use among others.