[bobcowan]

After the collector merge is the best place, so you're sampling from the entire bank and not just on cylinder.

"Weld the bung at least 24 inches downstream of the exhaust port outlet
(after the collector), or 24 inches after the turbocharger if so equipped.
The bung should be welded before the X or H pipe if so equipped"

"Using a clock as reference, mount the bung between the 9:00 o’clock
and 3:00 o’clock position. Welding the bung in the lower section of the
exhaust pipe can result in sensor damage caused by condensation
making contact with the sensor’s internal heating element"

http://www.innovatemotorsports.com/s...LM2_Manual.pdf

see page 8