in theory yes. but its main function is to reduce air so egr is increased. it would also help mix air and egr. so on a stock engine i would keep the swirl going.Yea i figured the same, so i did exactly that. Didn't notice anything different though. Might have to do some experiments.
Theoretically the swirl "feature" does improve combustion at low rpm. It increases the velocity of the intake air causing it spin around the combustion chamber.
however once you block the egr off its not really doing anything, its only reducing airflow into the engine. my testing way way back showed a slight improvement down low with swirl valve off (with egr blocked).