If you tune a double pumpers power valve the way Holley and some other sources say to then it maybe makes sense why they would also recommend a VS in many cases but if you select a PV based on cruise vacuum, or even just default to the 10.5 PV regardless “as a start” to fine tuning it I’d say not. There is a major difference between a power valve that doesn’t activate till you get heavy into the secondaries and one that does just on the primaries which is what you want it to do. Regardless, double pumper hands (or foot) down
