Did you figure out what the fluid was? I changed my lower intake manifold gaskets as well, I also used the "new and improved" Fel-Pro gaskets, and I also had a massive oil leak after. Frankly, I think the new design is just a recipe for disaster.
I changed the lower intake manifold gaskets 10 years ago as well, using a Fel-Pro old-design single piece gasket. Sealed perfectly that whole time and never lost a drop of oil out the bottom.