Stalls under load nearly new chainsaw ran great last fall this spring stalls under load starts and runs fine otherwise

Probably a lean fuel issue . Engine coolant temperature sensor reading warmer than it actually is causing a too lean mixture , restricted injectors, restricted fuel filter , weak pump or bad regulator on return systems causing too low of fuel pressure , Mass Air Flow contamination .

slight buildup in the jets will do this. I recommend 9$ seafoam 1/3 can to 1 tank of gas for three times in a row .this works 90% of the time before spending $$$ at a shop.also put a new spark plug even though it starts the old one could be fowling out.

If it is a 3.8 engine change the crank sensor,they go bad on the 3.8 engines.

Sounds like you messed with the spring that controls the governor. Check for that connection....
Easy to find, your throttle operates that lever that has the spring attached.

I suspect water in the gasoline.

Get some sta-bil fuel stabilizer. add twice the amount recommended on the bottle for storage to your mixed gas. Empty out chainsaw tank and refill with the new mix. Rub for 2 minutes, then shut off. Remove cover over carb and spray inside carb, soaking it down good and cleaning all internal surfaces visible - allow to sit overnight.
Next day
Spray down carb with carb cleaner for about 15 seconds. Start saw, allowing 2 minutes to warm up and reduce choke. If saw stalls, restart and spray inside carb as it runs with choke on - keep motor at the highest rpms you can as you spray - spray in 2 second bursts, not allowing motor to stall from spray. If it stalls, change sparkplug and try again. You have varnish build up in the carb and are trying to remove it so the carb will work without the choke. This may take some time but it is the exact procedure I used for my Poulan Team Realtree last spring - I spent about an hour spraying and staring before it ran without the choke.
Good luck!!

try cleaning your air filter. that should help. "BEEN THERE"

It had better do so--or any saw brand that fails to run on ethanol blended fuels will see sales fall rapidly in the USA. We, personally, own one of these same saws which (when new) ran great for about 3 days, then refused to start. A trip to the warranty repair station got us a new ignition module. After return, it ran for about two days, then would not start again. The warranty repair then installed a replacement carburetor and about a year later, still seems to be working fine--it's a great hard working saw when it operates correctly. Good luck!

Check for a plugged fuel filter and defective fuel lines. Make sure the carburetor fasteners are tight. Check for spark at the plug--it should be blue and snappy with a new plug. If ok, squirt in some fuel mix in the plug hole, replace the plug, and see if it will pop a couple of times. If ok, make sure the primer bulb draws fuel into it after several pumps. If still won't run, remove the lower chamber of the carburetor and check the diaphragm for flexibility and no holes. Hope this helps!

try replaceing the diaphram.