I have a relativley new Husqvarna 130BT 29.5 cc 2-stroke backpack leaf
blower and it has a stalling problem- runs for some time (maybe 30
seconds or maybe 5 minutes) then slows down and (usually) stalls or
sometimes speeds up again. It pretty much restarts immediately with a
pull. Fresh gas properly mixed with 2-stroke oil 50:1 as recommended.

Cleaned the gasoline pickup, tried loosening the gas cap in case the
vent was plugged.

Any ideas?

A lot of the small 2-strokes use pressurized tanks, so loosening the cap
is the wrong strategy with them.

Those that work that way often have a diaphragm pump that keeps the
pressure on the fuel; sometimes part of (or at least acting as a base
for) the carb. A sticky ball valve in that pump could cause what you're
seeing. Some use flapper valves -- more likely to fail sooner and
outright, but less likely to stick.

Lloyd