Dealer installed Jekill & Hyde Shorty (Euro 4) model with Smartbox 2 to my Breakout FXBRS few days ago and I wanted to share some information about it (when I was deciding to buy them, I just did not find any useful information about how they operate).

First, Owner's Manual is not telling anything besides that all 3 modes are legal --- which doesn't make sense, because Mr. Hyde mode is "straight thru" and pretty loud.
I found out how it's possible --- driving with the loudest mode (Mr. Hyde mode) with 4th gear within 48-52 km/h range (around 1600 rpm), then it closes valves automatically and is very quiet. I haven't read the regulations, but I assume that db measurement happends in this speed area.

Few other features I found out:
1. In two quietest modes, having WOT for about 1,5 seconds, valves will open automatically during acceleration and will close afterwards again --- which is very nice.
2. In quiet (Dr. Jekill) mode, driving more than 92 km/h, valve opens when you accelerate (don't need to be WOT). This is very nice as well, because you dont have much power when valve is closed.

So I can assume that Smartbox 2 listens speed, throttle position and/or manifold pressure from CANBUS to adjust valves when needed.
Sad that this information is not shared anywhere.