how many do i have? i went under my car again to inspect the rattling.

now, i've located the O2 sensor which runs into the exhaust pipe, not the manifold. it's pretty far back, under my passenger side compartment. now, the rattling is coming from a cylindrical type of thing that is up in FRONT of the O2 sensor, but I don't think that is my cat. (it's still located under the passenger seat area under the car, but farther back than my front wheels)

there's another shiny cylinder behind my O2 sensor that i believe is actually my cat.

or do i have 2 cats?

or is that rattling thing really a heat shield and the mechanic screwed up and thought it was my cat?

i know for sure that it's not my resonator, as the resonator is located even farther back, and then further behind that is my muffler.

please help, anyone. if someone could just look under their car for a moment or take a digicam picture or whatnot and let me know what exactly is what here, that would be great. the mechanic told me my cat was bad, but my own further inspection shows that it might not actually be the cat but just a heat shield.

thanks.
*update!!* I included some pictures here now.
picture 1 - This IS the cat, right?

picture 2 - What is this thing? Just a heat shield? The cat starts on the left side I think?

picture 7 - Another wider angle. The cat begins on the left, right? What is the rusted cylindrical thing on the right?
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'