I added the copper pipe extensions some time ago. They don't make much difference when you are idling, but when cruising, they are significantly quieter. The only thing I hear now is transmission and tires.
I'm glad you said that. The stock length piggy extension mod is complete and my first ride will be this Saturday. I surely hope you are right. I ran the two valks side by side, and I felt the 100% stock bike was much quieter at idle, and was surprised to the point I felt something else was drilled out.