Keeps Running Lean On Highway

[my1path]

This is driving me crazy, looking for some insight.

D21 MECM-131 ECU run with Nistune Type 1 ran fine for years on a VG30 with very little modification until recently...
Just installed a supercharged v6 bored out to 3.4L, Cams, internal coatings... the works...
Eclectically the main difference is Z32 N62 MAF and VG33ER injectors tested at 344cc (presumably 275cc @ 80%)
Note: No accurate FTS and FTL reporting with the D21 ECU (Per email from MATT 9Nov2020) and I believe resetting trims requires removing power (for how long?)

At low speed my wideband shows richer AFR's (as expected) under high load and boost. But when I get on the highway it goes lean. Increasing the K-value does nothing, its like it's stuck on o2 feedback or something. I set the o2 feedback temp to max and the fuel map rich across the board (approx. 12.5) and it still goes lean. It seems to start happening above 35mph and will not 'recover' until I get below 30mph. Really hard to dial in the K-Value like this, forget the rest of tuning or even think about boost.

I'm wondering if there is a high gear map that is not appearing on the list and after the the MAF/injector changes, the TP values are staying in the o2 region of this hidden map. Truck is also running a taller R&P than stock (3.7 instead of 4.3) this would theoretically make it enter high gear maps sooner.

My next troubleshooting steps will be to unplug the factory o2 and and unplug the VSS.