The bottom valve in this picture on the suction side of the pump (without the actuator) is set to restrict the flow on the main line. This will increase the suction head and decrease both flow rate and filter pressure plus it can cause the pump basket to leak air and draw in bubbles. Set that valve such that the handle is pointed along the common pipe and see if that improves things. BTW, do you know what those two lines go to (e.g. skimmer and main drain)?