Same 1500 mi trip, up at 7000'.  Noticed when I first started engine, it
would run slow, then stall if left at idle.  Then it was hard to start,
flooded.  Figured that it was the FI system pumping gas at a sea level
default until the O2 sensor kicked in.  If I kept the rpm up for 30
seconds it ran fine.

Except one day I pull into a parking lot, fully warmed, rpms fall off
and stalls.  A bear to restart, took 15 minutes, and that was with
cranking with the ignition off before turning it on to clear it.  Lots
of gas in the exaust.  After I got it started again, ran fine, 'till the
next day when it suddenly did it again.

????  At a loss, I decided to crank the allen nut on the air mass,
guessing that in was the right direction.  After being informed by
mechanic that it really is out, reversed direction!  Never did it
again.  Coinsidence?

TBill

***There is always one nut you don't have a wrench for.***