I'm not sure anyone has answered with specific reference to the V&H Pro Pipe you inquired about. I have one on my 06 Deuce and love it - it is not that loud at idle or low revs (unless you're really lugging it...) but if you whack open the throttle you'll hear it plenty! Not drag pipe loud by any means, nor, I would say, as loud as most aftermarket exhausts I hear out there. Overall, great performance, great looks (if you like 2>1s, which is a matter of some controversy), and medium sound.

Hope this helps.