Idle speed is only adjustment that may be performed on EFI system. Standard idle speed setting for EFI engines
is 1500 RPM, but certain applications might require a different setting.
But you might try a different governor spring location hole. Currently it should be in hole #3. But first make the governor is not stretched out shape.
To prevent engine over-speed and possible failure, a rev-limiting feature is programmed into ECU. If maximum RPM limit (4500) is exceeded, ECU suppresses injection
signals, cutting off fuel fl ow. This process repeats itself in rapid succession, limiting operation to preset maximum.
Now at 3100 you near max torque for the engine and any speed above that does not increase torque much at all. And 300 rpm drop from no load to load is just the normal governor droop.