Take a pic of the header and it's connections so that I can get back to you on your problem.......
I need 3 pics one to the head, the second one to the collector, and the 3rd one where the AIV port is on the header.......

 

Head



AIV



Collector


EGR

 

I see what the problem is with your idle.....
You will need to cap off where the sensor is at the AIV port( that is the second port to the EGR.
You will need a CAT, you don't have one, that is just a resonator after the header. Your original CAT was butted up to the mani of your old header.
The second sensor is used to read your emissions after the CAT has converted NOX and hydro carbon elements.
You can go to any muffler shop and get a bung made for after the CAT. Or just purchase an OBX straight pipe and modify the hole for the second sensor yourself use that as your bung. Best CATS for the price are theCATCO high flow cats, they work great, and you need it for your OBD2.
Your problem with idle is typical and I have seen it happen with guys that have decided to use straight pipe instead of a CAT on the OBD 2. You need the CAT and the second sensor has to be located after the CAT.....
So the first sensor need to go at the collector, and you need a CAT, then a bung for the second sensor......

 

lol good thing i bought that a long time ago!!

so the hole thats closest to the EGR needs to be capped, and that sensor thats in that hole needs to go to the collector? will that sensor reach all the way down there?

im going to the muffler shop tomorrow after school and get that cat put on. i'll mention to him about the bung too.

 

Yeah you need to move that first sensor down to the collector. Second sensor goes to the bung, just strip some wire and add it if you need too...

 

Wierd, once i took the car to the muffler shop to get that cat put on the idling has gotten better and the guy at the muffler shop said it wasn't really that necessary to create a bung unless i had a check engine light on.

other than that the sound has gotten a little bit better. sounds so good below 3500 rpms. but loud as hell past that.

Vin did you have to break your headers in until you got that permanant sound?

 

No I didn't have to break mine in at all. But you should move your o2 sensor away from the steering rack eventually it might break off, (cap that AIV). When you have time you should move them too the location placements that I described, it is better for your ecu to calibrate and you will probably run too rich with where the placement of the sensors are on the header right now............
If you want the harnesses and wiring to extend them longer you can order the catalogue from www.digikey.com it is full of Nissan OEM clips and harnesses....

 

lol bigvin, you said bung...

 

Bung without the hole........

 

aright cool thnx vin

 

No.... Thank you, atleast we all know that you can use an OBD1 header on an OBD2engine with some minor modification, (YOU PROVED THAT)..... It's pretty much a good know how, know to do type of thing.......

 

bigvin, you said you have a dc sports header right?

Well i went on dc's site, and they sad the s13 header was "coming soon" and only the s14 header was available... any thoughts on that?

 

UHHHHHH they fuc$ed up, or you misheard what they said.... My header fits for all OBD1 ports. The s14 OBD2 header is in the works and wont be out till next year.......
I spoke with Ken the tech advisor at AEM/DC sports........
Don't mention the dfifference between s13 or an s14 to a guy at DC they wont know what the frick you are talking about just give them the model year and call it a 240sx......

 

LOL.

 

BigV or anyone who gets to it first 4-2-1 One-Piece Header is what i want for a 92 s13 right? As i recall thats, and i might have missed it but what is the point of moving the o2 sensor etc..? Let me know thanks