Was there not something about this intake manifold gasket issue being caused by using the wrong kind of coolant, or am I off base here?
I think you are referring to the intake gaskets that had some plastic in them and the plastic was damaged by 2-EHA which is in Dexcool and Dexcool clones like "all makes all models". Once air got into the cooling system from the damaged gasket, sludge formed (Dex-sludge).