Such a product is not going to provide any noticeable gains on the 2.8L. The stock intake after the throttle body is too restrictive to see any gains, thus negating anything you do AFTER where the throttle body mounts.
If you want to see intake gains, you're going to have to modify the stock intake setup or pay for an aftermarket setup (both a lot of $$$$)
[This message has been edited by Fiero84Freak (edited 09-13-2013).]
To be honest, the throttle body spacer will be a waste of money. The V6 engine in the Fiero was tuned very well, and you would be better off with cleaning the exhaust headers and crossover restrictions out. How is your cold intake setup? Is it pulling air from inside the engine compartment? The factory system was a true cold intake.