Well the leak at the throttle body heat circ are of the upper plenum came back.
I followed JRS3800 advice and got fel pro intake gaskets, dorman upper plenum, and new hose for the inlet to the lower intake.
Definitely a demanding job. Changed out the lower intake manifold, and installed new thermostat and new sender for the temp gauge.
The intake gaskets were very damgaed and the nylon 66 material was very degraded at the coolant passages. Totally collapsed from the DEX COOL.
The lower manifold was changed by Pontiac a long time ago due to corrosion. I should have asked GM to pay the bill.