Good to know, thanks fellas.
The manual just had the basic generic info that I had expected. Even the official holley efi youtube videos were pretty generic about it, saying not to let the sensor get too close to the exhaust systems exit, and also mount it upward to avoid fluids puddling in it.
-I did get some good info over on the holley efi forums on a thread I typed up last night. Most importantly, that if I move the sensor more downstream, I might have to go in and adjust the sensors "advanced control" . Interesting to know. Apparently, even though the sensor sends immediate data to the ecu, that data is "old" because it has taken "some time" to reach the sensor after actually combusting in the cylinder.
here is a link to the thread:
https://forums.holley.com/showthread...-oxygen-sensor
See below for the photos of my new ebay headers and the dyno dons headers and you can get a sense of why I think that the sensor location isn't getting a true reading of all 4 cylinders... its just too close to the primaries.
New ebay headers with o2 bung location:
Old dyno-dons headers and bung:
see what I mean about how I just don't believe that a sensor located there could get accurate readings on all 4 of the primary ends? Maybe the two of them nearby the bung, but not the far two.