I live in the flatlands of the Midwest, at 1100 ft above sea level. I have made numerous trips to Colorado and other high plains areas - up to the top of Pike's Peak several times (14,100 ft), all without re-jetting carbs. My normal length of stay was 5-8 days.

I use 87-89 octane at home and premium in the mountains. I seldom got piston ping, except on very hot days (100F +). But, what happens at about 4,000ft and higher is oxygen starvation. Full throttle produces nothing at lower rpms, going out to pass on a 2 lane road is an adventure in patience - think VW beetle! Even with my 1998 V70 R, when the rpm wasn't high enough to let the turbo spool, giving it more gas meant going slower.

You will find 89 octane to be good with your compression ratio.

I would only re-jet if I were moving there. Remember, you need more air and less gas.
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My back feels better when I sit in a Volvo seat