Just bought new 08 1800N, fully stock no mods, added vtxexhaust.com pipes, now between upshifts experiencing a loud high pitch growling (like a semi coming to a quick stop), have spoken to several local mechanics, half say a fuel manager will resolve this as it's a product of a lean mixture, the other half say it's inherent with larger pipes and no way to get rid of it. I simulated a desmog by plugging the pair valve intake behind the air filter and it did not change anything. I don't think this is decel pop but could be wrong. No backfiring or popping just the loud high pitch growling between shifts. I've seen other bikes with this same sound and then others without it. Any feedback would be greatly appreciated.