I have run with and without, really no difference in drivability on an engine with a fair amount of cam. While some get away with it in the rear, why use one? On a drag engine the secondaries are almost always closed or wide open. Just one more thing that can screw up. Primaries I would use on a milder street strip car, but on a race only drag car with a fair amount of converter, I would leave it out. You have no chance of potentially inconsistent metering without. A circle track or road race car, it's a different story.