If i were to remove the precats and replace them with pipe would i still pass emissions and can i gut the cats with the o2 sensors and still pass emissions testing?

 

It would obviously depend on the smog laws of your state. In California, smog laws are so strict that even tapering or removing any smog devices can make the vehicle to technically fail the smog test by inspection alone. If it throws a engine check code, that too would fail.

But if in your state that visual inspection doesn't matter, and the guidelines follow just the emissions coming out of the tailpipe then here's one option. You can get a pair of 2-1/2" high-flow cats from www.randomtechnology.com and it will flow nearly as good as straight pipes and will do its job of burning the CO's and HC's. If you have downstream O2 sensors after the cats and you put straight pipes instead, not sure on this but I think it may throw a check engine light (CEL code) and cause it to idle rough.

 

Just saw your other post about adding flamethowers. Never mind my answer above. Flamethowers may not work with any cats.

 

you can gut your cats and still pass emissions.if they check yours by obd II its easy.just put a 1/4 ohm resistor on your downstream o2 sensor signal wires(the gray one) and it will pass perfect,trust me i just had mine tested and i only failed because i didn't have any cats on my truck,i figured i'd try before i actually put em back on.now i have the shells on and i'm retesting monday