Being there is a airchannel path between the wire and insulation since O2s need outside reference air make sure there is no kinks or crimping which would shut down that air path.

I find when people using the wrong length wiring they bundle up the excess wire and like tiewrap it thus again crimping off that internal airpath.

Exts are a joke since the coldest airpath is now gone as the wires used are common wires and not the special wiring O2s require.

The older the O2s are the slower they they function and response is slower.

A decent OBD scanner like I use comforms to EPA and does O2 tests and tells you if O2s are functioning properly and within spec window.

Biggest failure I see people do is having the wiring connected to PCM wiring harness and then when turning the O2s to get them on or off cause the wires to twist around themselves and crimp off that internal reference air path so always have O2 wiring harness free and let them spin as O2 is turning.