General AFR Guidance (Holley Tuning)

So, I was tinkering with it yesterday and swapped out the 6.5 PV for a 4.5 one since my vacuum in gear at idle is only 9.5-10". When I went to test drive it, I noticed a huge stumble when I mat the gas from a light cruise. Almost like the squirter is too small. It's got a 35 squirter in it. I swapped it out for a 37 with almost no change. Maybe it needs a smaller squirter for a longer pump shot. It was getting dark, so I didn't have a chance to put the 6.5 back in. I did notice with the 4.5, the AFR was really lean (as you would expect). It was 15-16 at light cruise vs. ~13.5 with the 6.5. I'm still thinking the accelerator pump circuit is causing the stumble, but think its weird that it only happened when I swapped out PVs. Could decreasing the power valve have caused this stumble?