Maybe i should have explained it better. The volumiser gives you more air, but at the same pressure, more volume. This gives the gun the ability to lower it's firing pressure, because it has more volume of air to use.
I can't gaurantee it will come down enough, you will have to try it and see. I've never actually done this just to see if it works, because it achieves the reverse of everything we try to do to guns, but it will drop the fps.
Remove the volumiser and put the blanking plug in. Screw the minireg adjuster fully in (not tight), and chrony the gun. If it hasn't come down enough, lower the dwell and chrony again.