Intake Manifold gasket question

[SoCalSlaughter]

So I have a 1990 Suburban v2500 5.7. The truck sits alot. I took the truck out to get its smog taken care of. The next day I noticed some oil dripping on the ground. I popped the hood and saw the front of the intake manifold was leaking some oil. While I had the hood open, I checked the oil level and noticed a small amount of milkshake on the end of the dip stick. I thought.. great head gasket time. Once I got the truck home I removed the oil fill cap and there was no sign of milkshake. With the truck running there was no bubbles in coolant. Removed all spark plugs and none where fouled or irregular from one another. I removed the intake manifold (Edlebrock performer), removed the thermostat and noticed it was a 190. I live in Southern Cali, seemed abit weird to have such a high temp. And noticed the intake manifold gaskets had the rear coolant ports blocked with the alittle metal block plate. But the intake manifold has the rear cooling passage. Im thinking the cooling system built up to much pressure and blew the gasket causing some coolant to get into the crank. Also, when removing breather hose from valve cover to TBI, the hose has some milkshake inside of it, just a film of it. The truck doesnt put out white smoke while it runs, it just passed it smog with flying colors, no miss at idle or anything