I agree with Hec. Focus on simple things that may have changed since you last ran the machine. In my experience, governors on those engines don’t typically go out of adjustment on their own.
If the operation bounces back to normal after momentary delays, I would not suspect a governor. You just rebuilt that engine last year correct? I’m assuming the internal governor vane checked out OK and you reassembled and set governor to spec at that time.
In addition to Hec’s advice, check for loose wires at the coil and loose plug wire, although fuel sounds like the culprit. Have you drained the fuel bowl and looked for water?