The lower the metering lever is set, the less time it will hold the valve open for per pulse which feeds fuel to the carbs wet end.
The low lever will have been starving the saw for fuel.
Get on Ebay and track down a MS460 carb. The walbro copy's from china are about $10. They have removable jets that can be plugged or drilled to adjust high side fuel flow.
You can see in the image below, they have a small L side hole (bottom left), a fixed H side jet (Middle Left) and a replaceable H side jet (Top Left) that can be adjusted bigger or smaller to fine tune the H side fuel delivery.
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