Thank you for the quick reply. They did provide the passing form. I filed a complaint with Arizona Dept of Enviornmental Quality and was surprised they actually called me. They confirmed the truck passed, but found it interesting the test prior to the passing one it failed for the same reason I failed. Unfortunately, they said there wasn't much more they can do. I suspect this I-10 Premier Auto sales paid the guy at the emissions testing center to manually enter the VIN, then ran another truck through the opacity test.
I found a guy on Craigslist selling a full exhaust (CAT and DPF) with sensors for under 1K. Supposedly it only has 40K miles on it. I'm making the 3 hour drive now to get them.
Thank you for the information on how the ReGen cycle works on the LMM, now I just need to purchase an EFI tuner and hopefully I can pass this test.
You are experiencing first hand about what happens when buying a used diesel. Kind of sad but if I was buying a used one it would be checked by a dealer to ensure it was in compliance and to make sure that there was no history of it being "bubbized" in the GM system..