Swirl valve Plug or unplug

[Jaybird]

Can anyone explain what the difference would/should be between plugged or unplugged.
I did the EGR mod sometime back and chose to unplug but the other day I plugged it back in and couldnt really tell if there was a difference,my wife drove the car and said it ran smoother. Maybe she was dreaming.
Thanks

 

[tweak'e]

swirl valve only effects under 1700 rpm i think it is.

 

[Jaybird]

Thanks Tweak'e