Although I don't have one, they don't even make one for the Losi XXX-NT I believe it should help. A torsen diff uses worm gears inside as spider gears and because they will only rotate in one direction they will prevent your differential from unloading. Power only goes to the side where the traction is. An open gear differential unloads. You ever notice on the 4WD truggies when they accelerate and pull up the front (or the front inside wheel comes up in a turn) how the tires just grow? Its because the open gear (even a limited slip) will unload and send the power to the side with the least resistance. Well, not on a Torsen. The power goes to where the traction is because the worm spider gears will lock and prevent the no traction side from unloading.
Here is a link showing a full scale torsen:
http://flashoffroad.com/features/Tor...rsen_works.htm
http://flashoffroad.com/features/Tor...RealTorsen.jpg