I have a 2001 F150 with the 5.4 V8, 125,000 miles. About 2 weeks ago when leaving a store the check engine light came on and I used a code scanner to see it had a P0171 code. I cleared the codes and drove since then with no light. Today, again when leaving a store, the light came on again; same code. In between the settings of the codes I bought a better scan tool and read more data. It shows high long term trim levels for both banks (18.5 bank 1, about 15 for bank 2). The code is set at low RPM, but shows engine load at 71% (which seems odd as I'm basically just off idle through the parking lot). I would expect a vacuum leak but idle is rock solid at about 600 RPM in gear at idle and the truck otherwise runs well. I visually checked vacuum lines after the first time it coded and they look good. Any ideas on where to start or common causes appreciated.

Thanks.

 

Vacuum leak at the PCV elbow behind the intake.