I don't know what other peoples opinion are, but in my opinion if you are racing, the powervalve does nothing. I mean if you have a 3,000 to 6,000 converter it's going into WOT from the get go. The power valve only pays attention when you leave the line at idle and opens up when the vacuum reaches what ever the power valve is IE: 4.5 7.5 for additional fuel. i personally donot run Carbs on any race engine but for the street the a power valve comes into play. If i were racing only i would block them off, for the street i would use a 4.5 let the fuel get there as soon as posslible.
just my .02
Zip.