I have a DynoJet Wideband commander I was given for fixing someone's ride. This set up has an in car gauge, and a plug and cable for a USB port

The car will have headers and an X pipe

I'd like to know how to determine where to weld the bung/place the O2. I know to point the tip down to prevent the collection of moisture and that I should have it close to the Header collector.

The system only appears to be able to support one sensor, I did buy two bungs JIK

So where should the sensor be installed?