A couple of things.
All the Ducati ECUs for the new monsters keep the O2 sensors in the loop until about 4500rpm i think. Therefore whatever you do to the exhaust cans have no effect on the AFR as the ECU adjusts it to keep it within that range. At higher RPMS it's moot as it's dumping more fuel in it. the lean is set from factory and is kept no matter the ECU (stock or DP) or exhaust.
BUT never go an open intake system/K&N filter without the DP map as that one is set for the more intake air conditions, the stock cannot handle it. You WILL run super lean then.
IF you remove the O2 from the ECU (Rexxer tuning) you can adjust that AFR accordingly with a better map, Powercommander or the like.
As far as these exhausts... like so many others, I think they are about 2-3 inches too long for bikes with the short tails. But they do have a very nice look and shape.