Spooky,
Check out these diffs from Wavetrac, click here =>
Wavetrac BMW. These are torque biasing all gear differentials.
There are a number of torque biasing diffs that are commercially available. Most have six or eight pinions. These guys use twelve 9310 steel pinions and have a transferrable limited lifetime warranty. They also use a patented wavetrac mechanism that allows the diff to dynamically apply biasing load to the pinions proportional to the traction available at the tire.
With their billet and forged steel construction they are among the strongest diffs you can buy as is attested to by their transferrable limited lifetime warranty. Interestingly the warranty applies to both street and race track use — sort of gives a peek into how robust the mechanisms are. Click the little camera in the BMW 188 axle listing for a pic.
I think you will find them to be quite attractive.
Ed