1994 Pontiac Bonneville. Head Gasket or Intake Manifold failure?

have a 1994 Pontiac Bonneville, according to everything I've researched (VIN & Year), it would be a 1st Gen. 3800 engine. It is smoking from the rear of the engine (or towards the firewall, rather)
as well as the tailpipe. It looks like a head gasket problem, but it has passed two mechanics leak down tests for head gasket failure. The smoke coming from the firewall side of the engine, materializes away from the block, coupled with the fact that there is a lot of smoke coming from there, I can't really tell where it is coming from, other that relative area. The smoke is white, and it smells like coolant, however the temperature guage doesn't budge from where it should be, and the smoke will stop eventually after driving the vehicle around a bit. I've heard problems from the intake/EGR scenario in these cars, but only on the Gen II's. Has anyone else had there upper plenum fail like this?? And could the head gasket still be bad even though two tests have come up negative.
If anyone has had this problem and fixed it, I would be greatful if you could lend some advice.
Thank you, Chris
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The Gen I engine is pretty sturdy.
Check the radiator and see if you are losing coolant. Sounds like a coolant leak to me.
The intake manifold gaskets on this engine are better than the later ones, BUT I tore one down recently and the area around the coolant ports was pretty degraded.
The coolant leak could come from a head gasket, of course, but it can also come from intake manifold gaskets, leaky hoses, corroded Welch plugs (freeze plugs), a pinched or degraded o-ring on the coolant hose neck on the manifold, and a number of other sources.
Get yourself a good flashlight and a mechanics mirror tool and you will probably be able to spot it with a little effort.
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