ok. i had my car on a hoist at work today. what you guys are saying is still kinda not making sense for one reason:

my cat back (from 2nd cat back) there is no 02 bung. The 2nd 02 bung is in the stock location on the flex pipe. if what has been said is true, i would have to put a bung in the midpipe after the 2nd cat for the 2nd O2 sensor, and extend the 1st O2 sensor and put it in the Flex pipe.

doing this would be 1 O2 sensor BEFORE a cat and 1 O2 sensor AFTER the cat. (this being the 2nd cat since the 1st one will be disappearing)

is this correct???

and....how would i go about having a O2 bung put into a pipe? Midas or somethin? The guy that i'm having do this said he's not too sure if he wants to weld into stainless steel...but he said he could.

thanks guys.

 

You know what? I'm an idiot!!!! I'm sorry dude. 02.gif I forgot that the #2 sensor is before #2 cat.I remember that now.It doesn't make sense that they did it like that,cause basically the ecu is not measuring both cats as it should.

Okay........................
Go ahead and have the guy put an 02 bung in the #4 header pipe.That will be easier in the long run.Then,the rest is still true.You'll need a bung in the inlet of the cat back for #2 02.Otherwise,the ecu will not see any cat at all,and you'll throw a code.

I'm real sorry about the confusion,my man.Can't beleive I forgot about that.

 

ok... here is something... on the SSAutochrome headers... they have two O2 sensor bungs built in... but like you said there is no cat in between them... so this is going to throw a CEL???? i am going to be buying a header soon and i dont want to be throwing CEL with this thing..... would the second O2 bung basically need to be plugged and another one need to be put in behind the cat????

 

Okay,this is my set up with never a CEL...............
(1)SS Autochrome 4-2-1 headers/down pipe
(2)OBX mid pipe
(3)Factory #2 cat
(4)Magnaflow muffler

The 4-2-1 I have came with an 02 bung in the #4 pipe.That is,the last pipe on the right.This is where I put the #1 02 sensor,and no modification was needed.The down pipe has an 02 sensor bung,which is not really needed.This bung came with a threaded cap,which I tightened down.Cat #1 is no longer.Cat #2 is still in place.If I remember correctly,the factory #2 02 sensor is located in the factory down pipe,just in front of the #2 cat.So,when you remove the factory down pipe you are no longer worried about the factory #2 sensor bung.Then I had the guy that installed my cat back cut a hole in the inlet side of the cat back pipe,which is directly at the output of the #2 cat,and weld in an 02 bung.Now, the wires for #2 sensor are too short to reach the new bung.So you have to cut the connector off,and splice wires in the factory wires,and then splice the connector back on once it's long enough to reach the new location.

That's it.The ecu is able to read #2 cat,which now is technically #1.No CEL what so ever.Just remember...................the ECU wants to see gases directly out of the header,and directly out of the cat.So #1 = before cat. #2 = after cat.

 

Yeah, and mine is the same way also but I have one plugged in the downpipe and have the threaded cap on the #4 pipe and have had no A/F issues or CEL either. The most important thing as Mad said is one before the cat and one after the cat.

 

ok. so finally. to sum everything up:

i have an 02 bung put into #4 pipe of header. the new Flex pipe's bung should be plugged, and i also need an 02 bung put in to the midpipe after the "#2 Cat".

this is rediculous. lol.

 

You got it!! Ain't it nice though when you finally understand something??

 

Yes it is. now i have to find a place willing to do welding on stainless steal.

does anyone know roughly how much i should expect to put in 2 bungs, extend 1 roughly 8 inches, and plug up 1 other bung??

 

glad you figured it out d00d. what a buttphuck that was eh? hah

that seems like a LOT of trouble to go through to me. my CEL is on and i was pissed when it happened - but i knew it was gonna' happen and still think it's not worth the trouble. i'll just fix it later. i want performance now! haha

 

Yeah,but it's better to do it right the first time.It gets to be a puta when you have to keep going over stuff.

Shark01racing....................................Y ou can plug the down pipe yourself.It should come with a threaded plug/cap.Just tighten it down.I had my cat back done at a Meineke,and at first they didn't think they could weld it.They tried a small spot and worked out fine.For them to install the mid-pipe,create a pipe for the end of the mid-pipe to the muffler,and install the muffler/tip,cost me about $190.The header and 02's were done by my dad and I at his shop.FREE!!!!!! :mrgreen: