390 VS or DP? VS can run a much smaller CFM demand as the secondaries can be tuned to not open enough to lean out or destroy the velocity. Just put in a larger spring. Put a paper clip on the secondary rod right up below the pot and take it for a spin with a WOT run. Come back to paper clip and see how much it pulled down the rod, thats how much your motors velocity across the secondary sense tube is able to pull the secondaries down. If you don't have the velocity you won't be able to pull that pot and secondaries open. Completely adjustable as well.
