OP @wwillson has the same exact problem as I do - burn off in high EGR temps, if his testing proves that HPL 5w30 Dexos D is indeed helping with burn, then I am sure they will get a few more orders for 5w30 Dexos D. I have tried different 0w20 brands of Dexos D-approved. My observations are non-scientific but I do drive same routes again and again across the state weekly, AC Delco was burning off most, Mobil 1 was slightly less (folks on forums say that Mobil 1 makes AC Delco Dexos D oils but I do not know if true, bottles certainly look very similar). With AC Delco I am 1/2 full on probe shaded area in 4K miles, with Mobil 1 I am 2/3 full after 4K. Of course different weather, season, speed, so many factors that are different but same trips. I wonder if @wwillson will be able to notice the difference in burn off with HPL. Watching this thread.
Even if Mobil 1 makes the oil for AC Delco that doesn't mean both sell the same oil. I'm sure they will blend your version of dexos D aswell, if you pay for it.