The dealer replaced the MAF and did two regens, one before replacing, one after. I left the dealer and the gauge climbed like crazy and went into regen around 15 miles. The dealer now just replaced something called a differential pressure sensor along with a sensor upstream and downstream, no change.
As to all of your other questions. Everything was perfect until 15,000 miles. I've changed absolutely nothing. Same fuel stations, usually Loves because it's hard to go anyplace but a truck stop with the toy hauler, Amsoil at 7.5k, new OEM AB filter.
I will reiterate, it was fine until around 15k and since then it's been getting worse and worse.
Talking to my service advisor he said his techs DESPISE working on the '19 and above Cummins trucks. Endless returns because they didn't fix it the first time. He said the Star techs act like they've never heard of any issues with the trucks.
I used to deal with this with my company that sold business phone systems. A manufacturer called V****i had tech support that would ALWAYS say "We never heard of that." Well, that was a total crock, we already knew a particular software version had a particular fault 100% of the time. Every single company that sold their phone systems knew what the faults were. We'd load different software versions knowing which ones had which problems and wouldn't affect a particular customer. Call in reporting an issue with a new version and they'd act like you were an idiot and it was your fault. We dropped them for a company called NEC that was very receptive to field techs input and rapidly implemented patches.
I think the difference was V****i is a US based company, NEC is a large Japanese company. It was obvious calling tech support, one generally knew less than we did, the other was staffed by very smart technicians and software engineers.
My guess is Stellantis knows the issue but it's cheaper for them to deal with repairs than to do a recall and fix the problem. This is a very traditional way for the manufacturers to handle things like this. It appears the Feds are looking at the K1 failures on '22s. How many of those guys had trouble with Stellantis getting it fixed with many out of pocket unreimbursed expenses? Stellantis KNEW they had a problem but said nothing until it couldn't be ignored.
Note: starred out the US company's name, don't need them to come after me. Any phone guy knows though.