Its the need for and the availability of higher octane which decreases in high altitude areas. I have had my Chris Rose (tillman) tune up to 9000 feet with zero issues. I wouldn't worry about it. Pick the tune which matches your expected driving style.
While the adaptive learning will make adjustments.The car will react to its altitude,air fuel ratio is what is important, and not taken into consideration by some tuners. I am at 6500 feet above sea level and my car ran fine,but the air fuel ratio had to be adjusted. I can tell you that you will be fine at the high altitude with the tune you have now. If you have a Air fuel wide band that would be ideal. The thing is that at high altitudes octane is 91 up here for the most part that is all that is sold; as far as the highest pump gas. Do you have a 91 octane tune? Some food for thought.
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