How come my troy snowblower stalls when I move the choke switch from choke to run ?

float in carb not shutting fuel off

you could try opening up the idle/mixture screw another turn to make the transmission from idle to throttle better
governors just open the throttle butterfly according to the spring tension setting from the throttle lever

You are having issues with you carb then. If you disassemble the weedeater partly then you will see to screws/adjusters sticking out. The one on the left side is the low idle, and the right side the high idle. You need to adjust the high idle side little by little. I'm talking a 1/4 of a turn at a time until desired results are recieved.

souds like it could be flooding out at full revs check the choke is fully closed

I'd say the carb is clogged somewhere, probably the main jet. The gas today is terrible. Removal/replacement may be the (only) way to go.

The carburetor will need to be cleaned very good. New needle valve maybe float and new gaskets That should take care of the problem.

Carb need to be clean if it set up a a long time

Take the belt cover off that covers the drive pulley on the engine. You should only have to loosen two bolts. Inspect the belt to see what it looks like. I am not sure if it drives a gear box or if it turns a friction wheel that drives the wheels. If the belt looks good check for shear bolts that might have sheared off and replace them.

Generally with two cycle engine as soon as the engine starts the choke needs to be moved to the off or open position. Some chokes have a middle position that lets the motor run until it is warm enough to move the choke into the open position. In other words weather it is a two or four cycle engine the choke is used only to start the engine. If you unit is newer and still does not run well with the choke in the open position, you may need to adjust the hi-speed circuit to a richer one.