Diesel, thanks for the nice write up. I have never seen my boost go to negative numbers (not sure it will on my CTS). I haven't monitored the atmospheric pressure. I find it strange that your car goes into regen at 18 grams. Mine, like PanJet's, starts at 22 grams. Any clue why the difference. I was driving mine last night when it rolled over to 22 grams, so I took your advice and continued driving until a regen was initiated and completed. As always, your information is really appreciated !