My take on “bigger” valves being put into heads that are less than optimum in the SSR area is that it usually makes the shortcomings of the as cast SSR form more pronounced.
Sort of the same thing happens when the PRP is opened without changing the SS. It exposes the other problems. The factory sizes the PRP the way they do for a reason.
I watched a Youtube video with Curtis Boggs and Jeff Hammond. Curtis talked a bit about monitoring pressure differentials (pressure drops) in different parts of the port to help really figure out what's going on with these low port heads. I think that would apply here.