Sounds to me like a big difference in driving style, maybe roads and confidence in your equipment. I feel much more comfortable now with the LSD in situations where I want more traction. The open diff never gave me a sense of comfort and I would be more cautious. The LSD unleashed more of what a BMW should be. The additional torque with the AA tune is what I feel more that an HP boost.
The additional torque combined with the LSD has changed the character of the car.
Agreed the 2K for the LSD is steep, but the added trust in my equipment is priceless.