Before reading further yes I know the collective of “there is no reason to invest money in the base models performance”. I got racing dynamics aftermarket headers and paired it with a 2.25” exhaust and RPM power stage 1 tune (the only one available for base &#128546. Seeing as how our N12/N16 platform have almost nothing available performance wise I have really gotten into studying air flow to see where I can harvest any potential gains even if it is only 1/2hp. From my readings it looks like long tube headers are the way to go. I’m down to be the nut that spends too much money on a custom set of long tubes but the issue I’ve come up with is the placement of the upstream 02 sensor. It seems to be what would keep this from being possible. Can someone more knowledgeable help shed some light on this? Thanks in advance!

This is my Baby

 

If you can extend the wiring down to where ever the collector end up, you'll be better off. You want that primary sensor to read all cylinders for best operation. Then, the secondary ("down stream") sensor can go anywhere, since your tune will have it rendered irrelevant anyway.

 

I have a long tube 4-1 header on an N12. Primary O2 location is just beyond the oil pan and secondary is somewhere past the first pair of hangars.

So i made two simple jumper harnesses (one for primary and one for secondary) that extend to the new sensor locations while avoiding hacking up the original engine wiring harness to get that extra length. All you need is the engine harness side plus O2 sensor side connectors, splice the ones for primary together using an appropriate length of wire, same for secondary and then plug it all together.

edited for clarity

 

Do you have a picture?