Exhaust rusted away.
For a thirty year old car this is a wonder of engineering. Acceleration beats most modern cars and the un-assisted braking is phenomenal - always straight. Road holding is totally predictable even in the wet.
I Do intend to upgrade to a Turbo when they become 30 years old.
Would agree with all that Stephen has written, the 2.7L would appear to be a much more responsive car than the 3.0L SC (probably a weight problem with the latter)
The first real, drivable (it corners predictably) super-car from Porsche in my estimation.