According to Walbro, the pump provides up to 8 psi fuel pressure. Make the pop-off too low, and the needle will never properly seat again with engine running. I experienced carb dripping at a 12 psi pop-off, so I quickly restored it to a higher 20 psi. At this setting the carb became very reliable.
Engine acceleration is the master of idle setting.
Whilst not standard procedure in gas engines, fuel line pinch may help to check mixture richness. If the idle still is too rich as shown by pinch, and the engine stalls at throttle up, then maybe the main needle is too lean.