A recent oil analysis turned up SI (silicon) of about 28 ppm for Amsoil ASL oil that had been in use for 12K miles. The air filter is not very old and is a genuine Toyota. No recent work done using a gasket sealer. I do not see anything obvious. Last oil change when SI was at similar level I found that the air intake temp sensor had fallen out allowing unfiltered air into the housing through a 1/2" hole. That was put back, but the SI is about the same. Anyone have any tips? Cannot see or feel anything cracked or loose. Question, what is the hosing that is below (but connected to with short vertical connections) the hose that goes from the air filter housing to the intake manifold.