Welding exhaust bung in pipe help.

Not all bungs are created equal,the type I sourced from carquest were not
scalloped on one side,and were stepped on the OD.The step would sit into an appropriately
sized hole,and it's depth would accommodate the pipe curve,simple enuff.The threads are a
little deep, so the sensor doesn't intrude too far into the exh. stream,but that's not the most
critical if it's just for tuning.If the bung is a flush-mount,I drill the pipe the OD of the THREAD
and use an old sparkplug to align it,then weld it in place.That way you're not welding the
heavier bung to the pipe on the edge,and you can flatten-pipe or scallop bung w/o affecting
anything,other than cleaning/chasing the threads if choosing the latter.
The really critical item is placement in the system, particularly if you are doing
duals, to get accurate & balanced readings.