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I have a 1997 Z71. Dual cats. Can anyone tell me for certain, if doing a cat back exhaust (dual mufflers into single 3" tail pipe) will trigger the CEL? And how about with shorty headers? thanks!
Well, let's think about this. Are there any sensors behind the split flange on a Vortec? Why yes there are. So, does your cat back system have a place to transfer B2 downstream O2 sensor?
Shorty headers are a decent upgrade over restrictive manifolds, but be aware of the need for proper EGR plumbing on the driver side. The tube is NLA.
As long as both up stream sensors are there, then should be ok. Down stream ones only monitor the health of the cats, but can be removed. I did it to a couple trucks, put spark plug non-foulers in first then the sensors, no more check engine light.