I suspect this issue has been done before but.....TFS has an EGR valve for my 84 at $75.95 while ebay has one for $16.99 Does anyone know what any differences in the parts might be? Made in China?

You often don't know until the fiero store product is in your hand. I will say this, however;
The fiero store does offer the premium part when multiple choices exist. If there are 5 EGR valves in production by different manufacturers, I would count on the fiero store sending the one with the best quality and fitment. They have an interest in higher quality parts and service. You do often get what you pay for!

Note what the Fiero Store has to say about their EGR valve: "The Fiero Store carries original AC Delco EGR units as an exact factory replacement."

Is the Ebay one an AC Delco? I doubt it. Note also that Rock Auto has the AC Delco part for $47.97. But if I needed one in a hurry I might be tempted by the Duralast EGR valve at Autozone for $54.