Starts fine, runs good above 4k rpm but bogs badly below 4k. Can take minutes of feathering throttle to hit 4k then runs good with max rpm near 7k. Anyone have insight into this problem?
+1 a cell pump not working.
There is a small check valve on the inlet to the pump that sticks.
This kills low end on these.
Try pumping the pump by hand while its idling. It should almost stall the engine if it's working.