!987 gl Backfires when reved up in park.Also hear puffing type sound and uneven exhaust blow out thru tail pipe.What is it?

Carbed or SPFI? If it's carbed it has Air Suction Valves that let air from the filter housing go down pipes into the exhaust. If the reed valves in the ASV's fail, you can get melted bits of plastic in around the air filter and backfiring issues.

 

Exhaust leaks can also lead to backfires in the catalyst, so find out where it's leaking from underneath and fix it. You can also block off the ASV tubes where they connect to the head with a quarter if you are in a non-emmisions test location.

!987 Gl Has 2 barrel carburator non turbo!

Probably an exhaust leak. And a rich condition.