A few issues - altitude related?

[hughseh]

So I'm the last week I've had 3 separate issues that I've never had before and wondered if they're related to altitude.

We're driving through France and in the last week have done Auvergne and then the Alps, so 1,000m plus altitude.

Firstly, the brakes are really juddering after more than a few seconds use, start to smell really bad and vibrate through the steering wheel. Coming down the Alps roads, not nice. Has to keep stopping to cool.

2nd -P0171 and 0174, twice,separated by a few hundred miles. Kills fuel consumption, the error code is apparently running too lean. Deleted both times and now hasn't returned for 100 miles.

3rd - low oil warning on the dash. Turned engine off and back on and the light had gone. Checked level whilst car still warm and was on min on the dipstick, but to be expected on a warm engine.

All issues need more investigation, but wondering if air altitude / pressure has caused these