How is the 2nd O2 sensor gonna check the emissions in the tailpipe if it is on the 4-2-1 header? With or without the race cat.

 

this is what he is talking about. neither of the o2 sensors go past any pipes with catacombs, so why doesnt this setup throw a cel?

wait, is it because one o2 sensor is only reading from one or two pipes and the other is reading from the entire exhaust?

redz, you will need gaskets for each connection you make down the exhaust line. email autochrome, they might be able to get you some.

 

Basically.. you plug the port in the header, hook the first O2 sensor up to the second port.. and then have bung welded into the cat back for the second o2 sensor.

 

Yeah I have no idea how the SS Headers work with where they have the bungs
It should be 1 before the Cat, and one after.

 

i think it looks at the change of hydrocarbons between two bungs.

if one bung is picking up the hydrocarbons from only one or two exhaust ports(check above picture), and the other one is doing it from the whole entire exhaust, then it sees the change as being good.