I have an 03 f150 screw with the 5.4, and I'm getting a P0172 trouble code.

I use the Torque app on my phone, and it tells me that the long term fuel trim for bank 1 is at -20 (or more) at idle. At the same time, the LTFT for bank 2 is +20. The trouble code is coming from bank 1 (too rich), so I don't think I have any vacuum leaks. I've checked my fuel pressure, and it's 35-42 PSI depending on conditions, which is within spec as far as I can tell (on the low side). The fuel pressure holds for 10-15 minutes when the engine is shut down, so I don't think I have a leaky injector.

I've paid a local shop to diagnose it, and they came up with all of the cylinders on bank 1 occasionally not contributing, indicating random misfire on bank 1, but its not bad enough to throw a code.

I replaced both upstream O2 sensors, and swapped the downstream ones, and none of that changed anything.

All of the plugs and coils have been replaced (another long story) within the last 6 months.

Anybody else seen this or have any suggestions?