If you can live with the noise, I would leave it alone. Your diff is working the way it is supposed to. They can add more LS friction modifier, but then you'd have less of the effect the the LSD is there for, mainly less torque lock up.
If your diff doesn't make any noise under any circumstances, then you have no way of knowing (other than taking it through an auto-x) if the diff is doing it's job. I'd take that little groaning noise as a sign your car is healthy.
Dinan compliment of stuff plus PF rotors and RG63s. Enough for now.
Why, yes. I am an abrasive bastard.