the vac pipe to the inlet is for pcv (positive crankcase ventilation) and does not work when you are on boost when you need it most (it is closed) it is there for drive by emmisions, hoovereing the crank. blank it off. I personally would vent the breather to atmosphere, as long as you blank the metering unit it will not effect fueling at all, it may even fuel more accuratly due to not having any leaks