What year, model, Fiero? Remember, ALWAYS ALWAYS state exactly what you are asking about. I'm guessing off of what you're asking though you mean the V6.
For all V6 Fieros, all the throttle bodies are exactly the same. OEM units made by Holley. The only differences is later on the "ldle set screw" as it's sometimes referred to was covered by a plug on later model cars (around 1987 this started happening). Remember though, this screw should NEVER NEVER EVER be touched. If you're having idle issues, you need to resolve why you are having issues elsewhere, not by adjusting the throttle body set screw.
The I4 engine's throttle body assembly (it's actually a fuel injector and throttle body together) setup was the same from 1984-1986. Starting in 1987 the setup was re-designed and slightly improved.