Poulan Pro 220 saw starts & runs fine when finger on throttle, will not stay at idle. Rplaced plug & same issues.

All you need to do is try to adjust the throttle idle speed or else a cheat would be to tighten the cable which means the cable will be pulling very slightly the throttle which means it will remain running when u release throttle.

Fuel starvation - 'lean fuel' condition
Basic things to check:
1) spark plug
2) spark arrestor in muffler
3) fuel lines and tank filter
4) turn adjustment needles out (counterclockwise) 1/4 to 1/2 turn
Chain Saws:
5) check impulse tube and intake boot for cracks or leaks
*if all of the above are OK and/or do not improve performance then:
Remove Carburetor
6) replace gaskets/diaphragms
a) use a spray carb cleaner to clean jets, holes, and body of carb
b) fuel pump diaphragm goes against the carb body,
then the gasket towards the outside
c) metering gasket goes against the carb body,
and the diaphragm goes towards the outside

I’m happy to assist further over the phone at https://www.6ya.com/expert/rolandw_c013176d62ee17ae