Did the entire plenum get replaced or just the UIM gaskets?
Maybe you know, maybe you don't:
The upper intake manifold ("UIM" a.k.a. plastic plenum) sits on top of a plastic framed gasket. That gasket (the "UIM gasket") seals the plastic plenum against the aluminum lower intake manifold ("LIM"). The lower intake manifold sits on top of the "LIM gaskets". The LIM gaskets seal the aluminum lower intake manifold against the engine block and the side of both cylinder heads.
New UIM gaskets help, but the plastic plenum doesn't hold up well to dexcool that has had prolonged exposure to un-metered air. Un-metered air can be sucked into the intake through the brittle/cracked plastic. If the plenum cracks there are two coolant ports right next to the EGR stovepipe that could dump enough water into your engine to completely destroy it; quickly or very slowly. Depends upon the severity of the cracks in the plenum. The wise replacement for the plenum includes a reduced diameter EGR stovepipe that doesn't make contact with the plastic, so hot exhaust gases can be shot back into the intake without dumping all their heat into the plastic.
Significantly trashed LIM gaskets may allow un-metered air, coolant, and oil to enter the cylinders.
When un-metered air enters the engine it can rob the engine of gasoline, which lubricates the upper portions of the cylinder bores. Less lubrication means more heat. All of the above contributed to my modest engine over-heating problems.
Just take a look, I caught mine before any major damage was done.
http://www.grandprixforums.net/lim-g...tml#post588679