I am running Arrows on a FAT DUC. Without baffles I needed to richen it up substantially, with baffles was pretty similar to stock to get same results. This is definitely unscientific, but my experience. YMMV.
For me, without baffles was just too loud for daily commuting.
Makes sense. With the baffles out, one has significantly less back pressure, probably a little less engine braking as well. I'm glad you brought it up, with mixture adjustments, there will be a difference, slight, but nonetheless. Now if someone can do a dyno run, it would be awesome. As far as the noise, I put mine back in as well, my neighbours are good people, don't need them being otherwise. There is a Harley owner that likes to rev it on weekends or whenever he feels like listening to it echo through the townhouse complex, I know how people feel about him.
![Dolph](http://ducatimonsterforum.org/Smileys/classic/moto.gif)