Final Resolution. Random Misfires.

Purchased HPTuners so that I could do a scan log of this SS and to make sure that it contained a "stock" tune in the PCM.
Verified that it was indeed a "stock" calibration GM file in the PCM.

Did several Logs of the vehicle. Found that no misfires would show unless the vehicle was running at a steady approx. 70 mph.
Intermittently, about 10 minutes apart, all misfire counters would max out and set a pending cel. What was interesting is the Log showed no other change in the recording other than the misfires (RPM, Power, O2 sensor) all remained steady.
Concluded that these were indeed "phantom" misfires. Decided to replace the PCM with a new unit loaded with the GM stock calibration.

Problem solved. Car has run great with no misfires in over 6 weeks.

 

Probably one of the pins on the connectors. When you plugged the new one in it fixed itself, maybe on the ECM side.

 

Thanks for taking the time to report your resolution. Now that you have HPTuners you can step it up a notch.