Nest some CPVC in the PVC. Then you'll have some shit.
No, you will not. The barrels are not where he put the PVC, they are in the gun. The faux barrel pushes darts back into the barrels then removes the barrier once you click it all the way in. If you put CPVC in the pvc barrels, you would have to rig up some sort of coupling system and remove all the pushback stuff from the faux barrel.
I removed the AR's first and that improved the range, but not all that much. Adding the PVC trapped the air behind the dart better than the 7/8" barrels on the gun and improved it much more.
I doubt that, there is no seal between the pvc barrels and the air output of the stock barrels to trap any air. If it works for you, then that's good though.