In the modern computer wizardy it does it all automatic. Once you get to Idaho Springs (10,000') you can't buy 87/89/91 gas anymore instead they sell 85/87/89. You can get away with lower octane gas at the higher elevation. Anyhow, those are some extreme elevation changes to deal with... Usually we put state or something so people know where we are for general troubleshooting. I have no idea what the elevation of KnightRider98 is so am just throwing out all the info.
I would bet you have a combination of issues, probably not adjusted right (should end up fairly close to the center of the adjustment range for most cases), possible wrong jets, but that is extreme altitude changes. If you bought a sea level vehicle and brought it to Denver you would / should downsize the jets for it's new life at 5000' higher altitude.