Sounds like stumble is ECUs attempt at Closed Loop (LP). Which Loop Fault code did you get?
Loop Fault Rich:
ECU Closed Loop Attempt failed, too rich to correct.
Possibly too large injectors, other fuel system imbalance.
Loop Fault Lean:
ECU Closed Loop Attempt failed, too lean to correct.
Possibly faulty o2 sensor, weak fuel pressure, other fuel system imbalance.
– TIP: This code is more common during cold weather starts as the first Closed Loop attempt may fail due to the Cold Fuel Enrichment value still being too high. This code can be ignored if the 2nd closed loop attempt succeeds.
This can be a PITA but INJ2 & INJ4 cavities on the ECU are C202_A3 & C202_A4. Check this connector, visual, make/break it.