Does this afr reading seem acceptable?

[azzhauler]

Just been wondering if this sounds ok to anyone else. I have a PLX wideband on my 01 C5, the sensor is in one of the rear O2 spots, still stock exhaust. At idle and on the highway both if I have closed loop enabled it seems to like to sit at a reading of 15.0:1. I figured running closed loop and allowing the front O2s to do corrections that it should read around 14.7/8:1, but maybe being post-cats it could read a couple tenths higher? Probably just reading too deep here lol, just wanting to make sure my wideband is accurate.

[WeathermanShawn]

I would not use that position (post-cats).

I got an exhaust shop to weld in a bung (pre-cats) for $20.00. You need high exhaust temperatures for an accurate reading. I think tailpipe readings itself has issues, immediately behind cats would most likely give you false readings.

That is probably why your readings are out of range.