Pardon me for showing what little I know about the ECM but ...
1. are all Fiero ECM the same just with different proms?
2. if I suspect that I have a ECM problem would it most likely be the ECM itself or the prom?
The reason I ask is that I think the ECM is causing my hard/no start and bad idle problem since I have replaced ever sensor I can think of. I have what I believe to be a good ECM out of a running car and wondered if I can switch them out to verify my thinking that my problem is in fact a bad ECM.
The ECM and prom have proven to be one of the most reliable parts on a Fiero. You should examine fuel pressure, wires, plugs, rotor, ICM. connectors, and anything else that looks old, before you worry about the ECM.
you have a V6? Then you should trouble shoot the cold start injector.