You need to data log your injector duty cycle to rule out the possibility that the ECM is not asking for enough fuel. If the duty cycle is at/near 100%, then the ECM is doing all that it can in requesting more fuel and no tune in the world is going to improve that situation.

Next up is to monitor fuel rail pressure while the afr is going lean. If rail pressures drop, then you do not have enough pump. If pressure stays constant, then pump capacity is not the issue.