that's why I didn't post immediately on your Q about the secondaries not being vertical as I am not 100% sure & was hoping someone with more knowledge would chime in but I would THINK that they should be wide open at WOT so there's no restriction then the weighted valve regulates the air. Set the initial (on manifold) then set the slots to 35 (vac capped) then mix/match springs FOR WOT then rehookup the vac adv & check it at a steady state high vacuum on the highway at an RPM above where the slots are maxed out AND just under the pinging point in everyday driving under varied vac conditions. I should check the 1406 on my 318 DD & look down & see if the secondaries are wide open at WOT and raise the idle to 750 & see if there's still no vacuum on the pass ported nipple