Did a search and learned things, but not quite any answers...
Bought the proper Denso Oxygen sensors for my 95 Z28 T56 I purchased 2 months ago and didnt know the age of the O2s, but now I know firsthand what the noise about installation is about for the passenger side front!
Thankfully, the drivers side front sensor was a breeze, so I installed a new Denso O2 there and dielectrical greased the connector, which fit perfectly.
I was not able to install the passenger side front O2 because my better tools and jackstands were loaned out and I drove her up a ramp, tried to remove the old O2 without u-joints and extensions but with the correct socket and muscle, but failed and left the old one in.

Now the Z has one new front and one old front oxygen sensor until I can get the car higher and use better tools and/or remove the y-piping. Started the Z this morning fine and drove to work.
The car now misses on more than half throttle in the higher gears, or at full throttle anytime between 2000-3500 rpm. The car ran fine before I installed the new sensor on the driverside.

Besides the disappointment in a poorer running car that I thought I was improving, until I get the other new front sensor in on the passenger side I wonder what caused the miss that feels like bad plug wires in my experience (the plug wires are recent, but again this problem started immediately after the new O2 went in... and ran fine until this morning).

Does the PCM have to 'learn' a new oxygen sensor for awhile after installation?
Does a Pcm/ign system get confused by a mix of working and non-working O2 sensors?
I know occasionaly a bad O2 sensor can be bad; should I swap in the other new one?
I carefully routed the new sensor's wiring and ziptied it; can an O2 harness touching a plug wire cause trouble?

Thanks yet again for any takes and help. Short-term until I can replace the pass side O2, will recheck plug wires and such to make sure I didnt damage them or make them touch other leads...

 

Any particular reason for picking the Denso sensors? Most people seem to get the best results with AC Delco or Delphi.

I'd also avoid putting anything on the connector. You are dealing with very tiny changes in voltage - millivolts. You don't want to inhibit electical conduction in any way.

Did you add any anti-seize to the threads? Were the thread factory coated with conducting anti-seize compound? Did you possible contaminate the sensor with excessive handling or anti-seize?

The PCM "learns" the long term fuel corrections based on the feedback from the O2 sensors. If you have a sensor that doesn't behave like the stock sensor, is not putting out the correct voltage because of a coating on the connector pins, is receiving high voltage interference from nearby plug wires, or a lot of other things, the signal will be corrupt, and the results will not be satisfactory.

Did you try removing the passenger side sensor when the exhaust was hot? That usually helps.

 

Thanks Fred.
Denso has a great track record in O2s, incl F-bodies, so I thought I'd go with an old standby. If the new Denso is the problem, ACDelco will replace it.

I put dielectric grease on the connector to the pigtail! From yr reply, I reckon I should unhook and clean with contact cleaner?

I used the copper anti-seize that came with the O2, and not much. Is it worth removing the O2 and looking at the bulb, or will the gases have blown off any contaminates? Is contact cleaner safe for O2 bulbs if soiled?

My son has many socket extensions and u-joints, and I will get his help on the passenger side; he was able to get bellhousing bolts out of his Camaro without dropping the motor, so his young, flexible, strong arms should help me extract that sensor!