Hi Lou,
No, I've only replaced the EGR tube which enters the exhaust manifold about 3" to driver's left from the oxygen sensor, PITA job. I did that on the '97 from below with help holding the top of tube. Some have done sensor from below but best done from above after removing coil pack. I will be doing the sensor on the Mystique come good weather (with exception of brakes I've become a fairweather DIY) and may also tackle UIM clean on '97.
BTW the sensor referred to in above post is upstream bank 2, on exhaust manifold next to rad, points towards oil filter.
Not clear, but you replaced the bank 1 downstream sensor (HO2S12) next to main catalytic? What code?
Your P0171 code probably caused by air/vacuum leak, check your cd. P0133 refers of course to the upstream (firewall)sensor (HO2S11) as noted by PA 3L SVT above.
Regards
p.s. Please call if you want to follow-up on above.
