Strange problem with 6-71

The blower can't make boost at idle, because the throttle blades are closed. So it cant get any air to pump into boost. Open the blades up, and that huffer starts puffing.
I run a 1400cc per rev toyota blower on a 1500cc in line 4 pushrod motor.(all non mopar obviously) The instant the pedal hits the floor, the needle hits 11psi. Everytime.
Does seem strange.
It can only be a leak on the discharge side of the blower. (Or a faulty gauge?) If the leak was on the intake side of the pump. it would try to make boost at idle. and it wold run like sh1t as there would be a lean condition. Actually it would be lean all over.
But if it's leaking on the discharge side of the pump, that charge must be leaking somewhere? And if it is, it's explosive! Even if it's the pop off valve, what's leaking out will want to explode at the nearest hint of a spark.
the only other thing would be a problem with the blower itself. Is the new pulley properly keyed onto the main shaft of the supercharger?
If not, the pulley might be going around, but the blower aint. Hook the carbs off, unhook the coil, and get a mate to crank the engine over while you look down the top. See if the rotors are turning?
Blowers rule. The torque never fails to make me smile.
Horsepower sells cars.
Torque wins races!