I tried moving the exhaust pipes and manifold evey which way. They are secure and don't touch anything including the heat shields, The noise is defenitely comoing from within as described above. I looked for the exhaust system in several online catalogs and print catalog. None show or mention a pre-cat. Is it sold with the main cat? If it is not sold seperatly it makes me wonder if it is indeed a wear item. Maybe these are only found in CA cars. Can debris get sucked back into the engine (disaster) if the loose metal is not removed? Can we keep driving the car with the loose innards? The car must me smogged periodically in CA so would cutting one out and replacing with straight pipe cause it to fail emmissions? They don't do visual checks, just tailpipe emmissions here in Los Angeles.

The left most part of this image also shows those so called precats (like little footballs just after the exhaust manifolds). I doubt they are only found on CA (50 state) cars. Maybe they only have innards for CA. I noticed that the online catalogs show much higher prices for the CA cats vs the 49 state cats,

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1972 450SL
1982 300D Turbo