Underdawg,
You're not understanding the various limited slips and what they do. Proper sports cars do indeed come with limited slip diffs. They help you in a corner by allowing the 2 wheels to turn at independent speeds. The amount of torque that gets directed/proportioned is also controlled by the LSD. As a matter of fact, the 911 does indeed have an LSD as an option. Same as every other sports car (M3, Corvette, etc). You would be hard pressed to find a sports car without one. The only reason it is not on the Boxster is because of Porsche's cheap ass. OOh, sell them stability control.
I don't know why you think an LSD would inhibit turning?
Perhaps what you're thinking about is a straight locking diff (found on 4x4's). These make horrendous noise when you're trying to turn. But they have their purpose for 4 wheeling as they assure a 50/50 torque split between the 2 wheels at all times, even if one wheel is up in the air while you're traversing rocks.
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