Bill,
Just my edjukatid guess, sunbirds are not really considered a 'hot" car, nor even a cool car. Even though, when compared to the much hotter car the Firebird, they got the name wrong- the temperature of the sun in sunbird is way hotter than the temperature of fire in firebird.
Anyway, thats why. When the GT turbos quit they junked them. Also, when the AT's quit on the non turbo GT's they also junked them. Mine is a MT, and they last forever.
Mine is a 1987 non turbo, GT. Only 7% of all GT's were non turbos. Yes, not as cool, but mine is still around. Low maintenence, goes along with low performance. But who cares about performance - at least mine is still running, at 210,000 miles, orig clutch, not a drop of oil consumption, and working ac. And with cops everywhere, who needs to "perform"?? LOL