As to the original Question, imho no functional difference between 2-window and 4-window power valves. Both are just to prevent the PV from being a fuel flow restriction. Very early Power Valves with the round drilled holes in theory could be a fuel flow restriction, so the 2 & 4 window units were developed.
The PV windows do NOT determine the amount of power valve enrichment. That is determined by the PVCR's, Power Valve Channel Restrictions, which are drilled orifices in the metering block itself, one on each side of the cavity that the power valve screws into.
Would imagine after the rebuild the Accelerator Pump Arm was re-adjusted? If not that might cure that stumble. The Accelerator Pump arm adjustment is directly affected by the idle screw adjustment. Any time the Idle Speed Screw is changed, an adjustment to the Accelerator Pump may also be needed. This is due to the Accel Pump Cam being mounted on the Bellcrank, change the idle speed screw, it moves the bellcrank, which moves the Cam, which can change pump arm adjustment.
Imho, the Primary Idle Speed Screw Adjustment should be done on the bench and set to achieve proper primary transfer slot exposure below the butterfly blades, only a 'square' no more. Then the accelerator pump and arm can also be adjusted on the bench. No the tricky part. Do NOT touch or adjust the Primary Idle Speed Screw again ! LOL Leave it right there where it was set on the bench to give correct transfer slot exposure...
The final idle speed once back on the car is done by way of the almost always overlooked Secondary Idle Speed Screw... which is a pita... but it can remedy a number of tuning woes.
It is a very small flat blade screwdriver 'set screw' with a 'played locking action' is one way to put it. It is recessed into the #10 iirc threaded hole in the baseplate.
This prevents the Primary Throttle Blade Butterflies from being too far opened at idle, messing up the Primary Accelerator Pump, over exposing the Primary Transfer Slots, and loosing all controlled of the idle mixture delivered by way of the Idle Mixture Screws... The Idle Mixture Screws get their emulsion from the same circuit as the Transfer Slots. The Transfer Slots are upstream of the Idle Mixture Screws. Over expose the Transfer Slots and all the idle emulsion discharges through them and nothing go past the idle mixture screws and the mixture screws no longer ahve any effect.
Here is an image from a Holley document about it.