Hello all, new to the forum and joined specifically to find out more about this PO299 issue. I have a 2020 dually 3500 with 16k miles on it and the truck is back in the shop for the 5th time regarding this issue. So far they've done the air filter replacement which I find funny since the truck was fine w/ aftermarket filters for 2yrs, but whatever. They've done the reflash several times, replaced a supposedly cracked EGR cooler, replaced a torn gasket (probably their doing in the first place from one of the other visits), and now even replaced the turbo itself and of course.......still not fixed. Just really disappointing and SUCH a complete waste of my time going back and forth to the dealership. Was going to try a different dealership, but after reading through all this it doesn't sound like that would do much good since once this deal pops up, sounds like you're stuck with it for the most part.