I have come to the conclusion that the rear two barrels on the Q-jet on my Powerwagon very rarely are used. Because of the NP435 transmission (granny tranny). The trans make it very slow to shift and has a really wide ratio jump from 2nd to 3rd. Its no problem passing someone though because of the 3.73 gears, you just push down on the pedal and easily accelerate, very rarely do the secondaries open. Sure I can mash the pedal in 2nd and open her up (and it is somewhat fun) but that shift into 3rd is a bummer. I've been at 70 mph on the interstate very easily (as fast as I care to go in the old girl btw) never even a hint of needing to use the rear barrels. Oh well, just saying.....(I've got a couple of Dual-jets, maybe I'll try one and see what happens, just need to make an adapter plate.) How much cfm is the Dual jet? (its just the front half of a Q-jet btw)