02 sensor question on headers-question for any m54

[lo_jack]

I have my headers mocked up, sitting on a couple of studs on the head. I have been reading a lot, and it seems like the e46 people put on headers, stick the fueling 02 sensors in the first available set of bungs in the collector and then disregard emissions. They end up hit or miss on check engine lights and their cars probably smell horrible if you sit behind them.

That seems silly.

One of the reasons I think this happens (besides not using cats, which is asinine) is that the 02 sensors in all E53/e46 era manifolds--the sensors that control fueling--are right off the head. No cheap header design replicates that, instead putting the fueling 02 sensor down at the collector. I believe this negatively impacts fueling and the ECU's expectation of data from the head.

So the question is, has anyone either A) not had issues with CEL/running badly with 02 sensors in the collector or B) welded a bung into the header 2" off the head, just like OEM to see if that would work better? I have half a dozen bungs and am in a place where I could mark up the headers and MIG in bungs for the upstream 02s really easily, and I might do that regardless of feedback.I am putting in good cats because ground level, smog-forming emissions and half-burned gasoline are carcinogens, and I like breathing.