Interesting. And we have been hearing about Quad 4 test mules for a long time.
The truth of the matter is that the Quad 4 was a stunning engine, for its time, but it was not well sorted.
They were loud and harsh, due to the lack of balance shafts, and they ate head gaskets like PEZ, it would seem.
But they still would have made the Fiero go like a striped ape.
To contrast, even the base non-DI 2.4 Ecotec makes 175 HP, or so, right out of the box, without any boost. (Sure, it's got its own issues, but it's light years ahead of the Quad 4.)
To go back to the technology available in the late 80s, look up "Delta 204T". It was the 2.0 Sunbird Turbo motor, made available in a few Fieros (dealer ordered). A handful of them made it into the wild.
Or check this...
https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20050818-2-060169.html