On long tube headers where should the o2's be? If you look in the pics I posted below youll notice it's located high. Shouldnt it be at the bottom where all the tubes come together?

 

On my Pacesetters, they are located towards the end of the collector. It seems unusual that they would have an O2 bung right on one tube only. You can always buy a couple of 02 bungs, drill out the correct size hole, weld in the bungs, and call it a day.

 

I have this funny feeling that this is the entire reason my car is running like crap.

 

Having the sensor way up there assumes that the one cylinder is representativ of that whole bank. Differences in airflow per port, fuelflow per injector, misfires, etc could introduce some error, but I don't know if it's an appreciable amount in reality.
I'd probably do what 2000GTP suggested.

 

One wire sensors (unheated) have to be placed the same distance as stock. The further downstream its placed, the colder it will get and the reading will be differrent. This should not be an issue with heated sensors.

 

ya, it should be in the collector,

 

sssalah ~ The computer will adjust for that through the BLM's

I would rather have it down at the collector, that way if you DO have a problem with one, two, or three, of the other cylinders on that bank, the sensor will read accordingly.

I would grind them off, weld it shut, and drill & weld new bungs on to the bottom.

What brand headers are those? They look like they have decent welds/flanges etc. but that is just dumb with the O2's there. I wouldnt trust it.