somehow I missed this one, been off line for a few days, and it sounds like you have a handle on the situation.
A few after thoughts.
Holley 94's are known to have an odd sized PV gasket, and many non Holley gaskets don't seal properly, causing an over rich condition.
while many people have for many years plugged off PV's and raced very successfully, it causes the engine to rely on the main system for part throttle A/F ratio, and because the main jet has been increased to compensate for the plugged PV, you are now driving around at part throttle in an over rich condition with a (usually) colder heat range spark plug which may adversely effect the engine when next asked to go full throttle. I found that by installing a vacuum gauge permanently in the dash, and noting vacuum at idle in gear, at idle at staged rpm, an at full throttle crossing the finish line. with the vacuum readings noted you can determine which PV to use, you want it closed at idle, closed during staging (usually higher than idle but controlled for staging) and open at full throttle. with these tiny carbs there is the chance that you may build vacuum in the manifold as you near the finish line if the demand for air is high enough below the throttle plates and the carbs are a restriction you could see a rise in manifold vacuum high enough to close the power valve, resulting in a lean condition.
So, what does this all mean, I prefer to keep the power valve in play, as driving the car around the pits and staging area is done on a lean and clean secondary circuit, which keeps the plugs all shiny and clean. It takes a bit more tuning up front but once set it will make life tons easier.
the zoomie headers while zoomie looking, detract form the low rpm tuning of this set-up, they would be perfect in a clutch set-up that left the line at 5000 rpm. with a torque limited trans like the PG (its like starting out in second gear in a 3 speed) and no trans brake you need all the low end torque you can muster. a proper length 3 into 2 header would be way superior to the zoomies. UNLESS the zoomies kill enough bottom end torque to make getting off the line with hard 6" street tires easier.
just my 2 cents.