Yes, definitely sounds like a jetting issue if the stutter is only occuring at altitude.
The first thing I'd be doing would be to compare main and pilot jets, needles, needle positions and pilot screw adjustments between the two bikes.
I do recall when I was up in the Andes that I had breathing problems in all gears at anything above 6ish, so no surprise here.
Garry from Oz.
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Garry from Oz - powered by Burgman
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