I'm in the same boat, and I've just given up and drive in L9. The noises that my 6.2 makes relating to DFM are frustrating and embarrassing. And, like you, I've driven at least 6 other 21/22 Tahoes/Yukons/Suburbans with the 6.2 and none of them made the noise. I wonder what Cadillac's response is when someone who has spent $120K on an Escalade comes in and demands that they get rid of the noise.
I did contact Range Technology, and they confirmed that they don't have anything yet that will work on our vehicles. I really hope they come out with something soon.
My truck is currently at its third dealership.
The first dealer that actually tried to address it took $120,000 escalade out and said that it squealed just like mine just a bit quieter. It wouldn't let me ride with them. I just had to take their word for it.
At the second dealership I drove a 6.2 l Tahoe Premier and it also squealed at stops but not during the shifts or on the highway. It stops on squealing was dramatically quieter than mine.
The current dealership that it's at is telling me that none of their vehicles on their lot experience that squealing and that it's absolutely not normal, and that they're going to take it up with GM. Let's hope they do the right thing.
But according to the TSB there's absolutely no fix.