OK, looks like you posted an update while I was typing my last response. So the low end power change was due to the PV. Where you able to observe a difference in the low RPM AFR at WOT with the different PV in place?
" Do you think that the 13.0 is a safe WOT reading at the shift point? "
I have always heard that the typical motor will like somewhere between 12.8 and 13.2 at WOT. At this point, I think the only way to really refine the best WOT number would be on a chassis dyno or dragstrip. You are likely very close though, and only you can answer if further tweaking would be worth the effort. If you have screw-in PCVRs you could increase your WOT AFR without further disturbing your cruise setup.
With respect to a second wideband, here is something to consider. I have two bungs but only 1 wideband. I move the sensor from side to side periodically. This made some sense when I had a single plane manifold on it since one side of the carb will have more influence on one side of the motor but now with a dual plane, one side of the motor is already feed from both sides of the carb so it is hard to really know whether the motor wants a staggered jetting. Best bet is probably to check the plugs and see if all the plugs on one plane look the same or different from the other four.
I am very impressed with how well you have done with your tune. Well done!
