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2012 Sierra (and all new gms) front and rear cat differences?



Just wondering if you know on gm vehicles with two cats inline if the factory cats are different. I notice there is no o2 sensor behind the second one. Is one oxidizing and one reducing? Or are they both the same? From looking the rear has slightly bigger holes. Sorry the question is a little odd, It is for using stock cats with headers and o2s I can't figure out who else but a gm tech would know the cats difference.

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Nope I'm sure they are cats. The first are right behind the manifolds and the second is after the pipes merge right by where the y pipe clamps to the catback. They both have grids inside them, although the back one appears bigger holes in the grid.

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