Can't pass emmissions

[stock1g4g63]

Hey guys, I couldn't pass my emmissions here, and couldn't figure out what it was. I'm no wiz, but I've changed back to stock injectors, stock downpipe (I actually have 2 cats as of right now, for the emmissions.. i won't get into details as to how), running stock boost, and have all my afc settings back to zero. I no longer have too much fuel, but there's still too much CO coming out of my exhaust. The guy said he's pretty sure it's my 02 sensor. So which one is it usually? the front or back one? Because I really don't have the money to go buy both, if only one will suffice to pass emmissions (my check engine light is on as well).

 

[stock1g4g63]

Well, it turns out one of my friends works at an auto parts shop and can hook me up on the front one (for free...). This'll leave money for the back one... but we'll see.

 

[Eclipsemblue]

make sure your ERG is recycling the shitty exhaust gasses, not good for the engine but in order to pass those gasses must recycle back into the intake manifold, if ur ERG is clogged the shitty gasses are flowing out threw the exhaust causing you to fail.

 

[stock1g4g63]

ERG? is there anywhere I can find a diagram or instructions on this, it's the first i've heard of it . that sounds like it could be a problem or at least part of it...