Yea, those need to be plugged in, unless they are taken out of the tune completely (deleted) or modified w/foulers or non foulers. Those aren't just checkers as you may think. There's more to those downstreams.

 

how come nothing changed when I unplugged them? what else do they do?



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Keep running it that way then

It doesn't bother me..

 

Well you at least certainly don't want to run around with those O2 sensor mount holes unugged...

 

thanks everyone for your advice.. I took it to the shop and had a pressure test done and found out my rear cats are plugged so I'm just gonna have them replaced with pipe and leave the fronts in



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Well reading up on this I just found out the info I had before is incorrect and my custom true dual dump under truck rear cat delete might be fairly not bueno. Sounds awesome and feels the absolute same. Guess I'll try the gotts mod and weld in bungs in my new piping I replaced my rears with. otherwise I made sure to keep my stock rear setup somewhat intact so I could weld it back on in case of emergency. Thought that the downstream O2's were simply cat efficiency checkers and the fronts were for A/F ratio checking/correcting. Correct me if I'm wrong, would like to have someone at least answer the O2 sensor question for me if someone could.

 

Oh and I obviously left the rear O2's unplugged because of my incorrect info that I gathered and the fact that my new piping didn't have a bung in it although it's my plan to weld one in asap anyways. and it is throwing codes, have to check what they are tomorrow.