A few years ago, I found myself in a familiar position as a car enthusiast: Shopping for an NA Miata. My criteria was simple and typical—I wanted one of the later 1.8-liter cars (for their extra torque), a rust-free chassis (not a given in the Northeast), a manual (duh), and a limited-slip differential. The conventional enthusiast wisdom is that you always want an LSD, but back then, I couldn’t quite tell you why.
