Good day Folks,
I was in error about one of the codes, it was P0455, which is a vacuum leak. The problem was the purge & vent solenoid. When checked, it worked electronically but wasn't working mechanically. My E-mail to GM customer care paid off. It only took about a year and a half to find the problem. But and there'* always a but, GM in their infinite wisdom set the operating parameters for the vacuum monitor to work at 4 to 30 C. This in a vehicle for North America. It still can't get the test passed because of this one monitor. I may have to take a trip down south. Thanks for all your help and suggestions.