Elevation Changes

[No Rice]

If a car was tuned at a elevation 650ft with humidty at 50% on avg and on 93 octane, would you have to retune if the car was now living at 2100ft, low humdity in the teens or lower and now 91 octane?

[6Speeder]

No, the change isn't that great. The PCM will compensate for it easily. I had mine tuned at sea level, now at 6,000 ft altitude, I adjusted the air fuel by 1% to match what I had before. And, at altitude, the 91 octane fuel is as good as 93 @ sea level.