Update - based on what the short term fuel trims (STFTs) were doing during the stumble, I added 13% fuel across the board to 400-1000rpm and 45-100kPa and then smoothed the 1200rpm line 45-100kPA into the 1400rpm line. I also changed the EGR min/max rpms from 600/2400 to 900/2500. The stumble has gone away although I did discover the car has a cold misfire under load that was masking the solution. Gotta go chase that now too. But.. once warmed up, the stumble appears to be gone.