I'm not sure the intake manifold gasket will allow water into the sump. I guess if the valley gasket fails or the manifold is very loose, water could get into the vee.Other than head gaskets, bad block or intake gasket, is there any other gasket failure in the engine that could allow coolant into the oil?:dunno:
A cylinder leakage test will tell you if you have head gasket failure, and where it is. Leakage testers are fairly cheap at Horrible Freight and I find this an essential tool for troubleshooting engine problems; moreso than a compression tester.
A cooling system pressure test will tell you if you have a leak somewhere in the system, but will not pinpoint it's location.
All that said, if you have chocolate mousse in the sump, that is not a good sign and it probably does indicate a head gasket leak.