boost vs. a/c?

[Kerry Griffith]

After another few years of lurking, I've got a question for the collective
mind:
What causes my a/c to blow from the defroster or the footwells under boost
in 5th gear?
This manifests when going up hills. As soon as I take my foot off the
accelerator, the a/c blows from whence it should.

A possibly related symptom: When warm, the car will stall upon restart w/the
a/c on. Problem is lessened by starting w/climate control off.

TIA,
Kerry

Hoppen stage 1, RS2 em, 106k