Help with mysterious P219A code!

[Skyhigh]

2021 Ram 1500 Limited 5.7 HEMI 83k
89 octane

I’m chasing an intermittent P219A (Bank 1 Air/Fuel Ratio Imbalance) and looking for ideas before I keep throwing parts at it.


Symptoms:

• P219A keeps returning
• Usually comes back during steady cruise around 1500–2000 after clearing code
• Very slight off-rhythm vibration/shake at idle, but it’s subtle enough that I only feel it with my hand on engine
• Truck otherwise runs well
• No noticeable power loss
• No rough idle
• No misfire codes
• At WOT around around 5k rpm I sometimes hear something like a little chatter the same as running low octane

Things I’ve already replaced:

• Upstream O2 sensor on Bank 1
• Exhaust manifolds BD diesel
• All spark plugs
• One fuel injector (suspected Bank 1 injector)

Things I’ve checked:

• MAP sensor voltage looks normal
  • KOEO around 4.3V
  • Idle around 1.08V
• Fuel trims appear normal
  • Idle:
    • B1 STFT about +2.5%
    • B1 LTFT about -0.6%
    • B2 STFT about -1.4%
    • B2 LTFT about +0.8%
  • Cruise:
    • B1 STFT about +2.7%
    • B2 STFT about -3.7%
• No obvious vacuum leak symptoms
• No obvious exhaust leak symptoms after manifold replacement
• Misfire counters on cylinders 1, 3, 5, and 7 remain at 0 even after about 30 minutes of driving
• Fuel injector all operate at same voltage.

If anyone has any ideas I would greatly appreciate it thank you