Figured I better answer my own question in case anybody else is searching for the same problem. Short answer is that the replacement turned out to be the wrong sensor. The car is registered as a 2009. The VIN number checks out as a 2009. The GM dealer looked up the Delco part number for that VIN and it cross references to the NTK sensor I used. My brother in law was looking at pictures online and noticed that the retainer clip for the wire on my original was the same colour as the NTK for 2007-8. I checked the manufacture date on the door panel and it was May 2008 so if it is a 2009 it is a very early one. On spec I tried the NTK sensor for 2007-8 and it cured the problem. It has been over a week and there are no codes and no pending codes. Glad I wasn't paying the dealer hourly rates to fix this one!
Brian