i finally got my exhaust off my car today and i noticed theres like a little throttle plate like thing that goes between the stock manifold and the y-pipe. there are some connectors and linkages, i didnt see where they went to. what is this thing? it honestly looks liny a tiny little throttle body that blocks off the exhaust flow..

 

That's your THERMAC valve thingy. It uses the hot exhaust to warm up the intake while the engine is cold, then it closes. Some of the carb guys will chime in and give more details on it.

 

It closes off one manifold and forces exhaust from that side to flow through the exhaust crossovers in the head and under the manifold to warm it up.

 

EFE valve (Early Fuel Evaporation). Does what rsn & Ape said. Operated by a vacuum diaphragm.

Haven't had one on mine since the headers went on in Nov '01. No particular issues w/o it.