I don't know what your looking at. The only way coolant can get into the exhaust is if it leaks from the water jacket into the vacuum area.
I looked at this design again and it looks like the lower gsasket is the only possible place.
The only pklace there is coolant is in the cooling jacket that runs through the metal manifold and the only way it can get into the intake is through the wall of the water jacket or at the gasket.
Pull the manifold and change the gasket.