For reference, I live at 711 ft (+/-) above sea level, and am jetted with a wideband Lambda meter.
I've driven my car from here to Kalifornia on I80, across Nevada on US50, and up from San Luis Obispo to Las Vegas on CA58 and I15. I've taken the car all over the golden state, from sea level on CA1 to over 9000 ft in the Sierra Nevadas.
The car ran great pretty much everywhere at sea level and across the high plains, a bit rich over the Donner Pass, and would barely idle at the Yosemite east gate at Lee Vining. I never touched a thing, and the car ran well up to about 7000 ft.
The problem really, really has nothing to do with jetting for 3500 ft of elevation.