Dan,
I highly doubt it is the intake and it is more likely the head gaskets. Do not run it with coolant in the oil. It will destroy the bearings. Get that shiit out of there fast.
Check the coolant overflow bottle for bubbles if the engine is running or the smell of exhaust. You will also see carbon in the coolant which looks like pepper in the coolant.
If you look at the spark plugs, the offending cylinder will have the spark plug looking like new as the steam cleans all the fouling off. If you have none of those symptoms, it could be the intake.
