It has nothing to do with reducing sound. Its all about exhaust tuning/flow at specific points, and remains mostly open during operation. Everyone that's removed it (including myself) cannot tell it's been removed. You have no choice but to remove it when going to a slip-on. This will only add...
Get the Duken4evr map pack. Inside it there is PCV section that contains smoothed stage 1 maps. Look for the Whittlebeast stage 1. This map made my bike run like a missile. At the time, I was running a slip-on and K&N. The PC5 will also require "acceleration enrichment" enabled - 50%...