The water ports of my raw water exhaust manifold are clogged with a thick, pasty grease material that only lets water trickle through. The ports are not clogged with rust. I've tried carburetor cleaner, Prestone radiator flush, sulfuric acid, lye, Dawn and CLR. Only the CLR seemed to help a little but the flow is still minimal. I looked for a radiator shop in my area but none have the equipment to clean out the manifold. The ports are too small and twisting to use any type of snake. Other than replacing the manifold, any ideas?