General AFR Guidance (Holley Tuning)

My 570 ran awesome OOTB but the 670 ALWAYS had that stumble as soon as I hit the gas. The 570 runs 2X better than the 670 on a 360. I ended up sending it back to Holley to see what the problem was. Said the needle/seat was sticking and replaced those parts. I still have to bolt it back on and see if its fixed. They "flow" it to check them. I also use a wideband A/F and it wasn't much help trying to get that thing right.