Join Date: Feb 2017
Location: The Mini Apple, USA
I don't have these particular pipes; however, I've changed exhausts on over a dozen bikes. What you are describing could be an exhaust leak, which can be pretty easy to diagnose, but will require an extra set of hands.
To test for a leak, turn the bike on and have a partner block off the exhaust hole(s) with sturdy cardboard or pieces of wood. The first thing to do is listen to the change in the exhaust note. You may be lucky and hear a pronounced sound of exhaust escaping from the area of the leak. Absent that, go join by join feeling and listening for a leak. You'll likely find it pretty quickly, but I'd advise not to stop at the first leak you find.
Once you have the leak identified, remove the fittings to that point, apply exhaust join cement/compounds, and reassemble/retest. I've had this happen a handful of times and fixed it every time.
I go for the whole "dark and mysterious" thing, but usually settle for confusing.