In the end not selling enough V6 cars did the F-body in. If you will look at the raw numbers you will see they sold about the same amt of V8's every year.
Problem was the V6 cars were too blaa, too vanilla and nobody cared. The 5th gen V6 needs to be stylish (they have that covered) and loaded with cool stuff. It has to be a gotta-have package.
The 4th gen, in the end, was just a motor in a box...a sleek box at that but w/o the big motor it was a pretty ho-hum car to the average buyer looking for a coupe.