Is the gun one that you added porting to and changed nothing else? If so then you can make the point that porting is giving you better scores. But if it's a different gun, different stock, different load or some other change then any or all of these factors may equally be part of the improvement if not greater.
Both barrel sets of my Beretta 682x were ported after a ShockMaster was installed.
Perazzi Mirage was ported before the addition of the JS Air unit.
Perazzi SC3 was ported by the factory but has custom wood.
Perazzi MX8 is non-ported but has custom wood.
Remington 1100T (rainy day gun) has only been ported (2 barrels).
Only the 1100 has factory wood, the others have been altered. With my primary comp guns having recoil reduction systems, there isn't a noticeable change in recoil; however, I do feel that I can get on the second shot quicker with the ported guns. I've been using the same recipe reloads for years. As you mentioned earlier, it's hard to know how much is between the ears.