The use of a power valve lets a carb (Holley in this case) be set up to run leaner during normal everyday to the market/school drives for more effiency but will richen up the mixture equal to 5 -6 jet sizes at a low vacume which occurs at higher throttle positions-

These days-------fuel sucks, no such thing as vacume(well if there was a perfect vacume there wouldn't be anything so evedently there isn't any such thing as vacume)

How much etonal does your fuel have in it? If you are racing why not use 100+ race fuel? For racing you could lock the advance in dist and only retard it for starting--

Have you verified tdc and all the markings on your crank pulley???