Recieved and installed MIVV Suono for my 620, ordered from PJ's, took just over 3wks.
Installed in a jiffy.
Absolutely no rideability issues, same idle etc, bike might feel minutley smoother at 5K, could be my imagination. (Haven't done a TB sync, bike runs great).
SO much lighter than stock, so much shorter, was really getting tired of stockers especially with the chopped tail on my bike.
Someday I'll figure out how to post audio - bear with me as I attempt a pic:
These sound a-m-a-z-i-n-g, really not tempted to remove baffles.
No popping and whatnot, just just a nice loudish growl, deep but not boomy. I can hear them at all speeds, unlike stockers, drowned out by wind at higher speeds.
OK so it seems I'm failing at imbedding an image - hope you're not required to login to see:
http://www.photoshop.com/accounts/8ea205126e8348a19b3b78c5f1e69248/px-assets/594f74a3b7184e9e8eb0f010a8033546