Thanks for sharing.
P061B, yeah I don't know what causes it.
Obviously if you find a fix I'm happy to listen to your whispers.
I'm pleased you haven't played with boost as I'm wary of the stock turbo's reliability and when I did a calc a while back it was pushing almost max airflow (random thought: I wonder if there's a trq calc based on airflow that generates the P061B?)
Wow, given the way trq drops off a cliff at 3000 (stock) I'm surprised the tuned trq curve so closely aligns given the AFR info. I'd assumed the AFR would start going lean at 3000, not 4000. It IS a little turbo, though.
Looking at air again... maybe consider the following? (yes, I mix my units. I'm a metric transition child)
ECM10293 - bump the 85.1kPa line up 4psi
ECM11885 - bump the line by 25%
ECM10354 - bump by ~4psi (since you're getting to 24psi now)
ECM10307 - 'might' have to bump this by 4psi because of ECM10354
Caveat emptor!