P0171 Lean Bank 1 Diagnosis on 2000 GM 7.4L Vortec Engine

I own an RV equipped with a 2000 GMC 7.4L Vortec engine (50,000 miles) that intermittently triggers the P0171 fault code indicating a lean condition in Bank 1. Notably, I am not seeing the P0174 code for Bank 2, which suggests an asymmetrical issue. At idle, both fuel trims are at or near zero. As engine RPM increases, Bank 1 fuel trim rises above Bank 2, though it never exceeds 10%. I have not yet tested under load due to the vehicle's high power output and lack of a helper. Several sources suggest that a malfunctioning MAF sensor could trigger both P0171 and P0174. However, given that only Bank 1 is affected, this seems less likely. My current scanner does not provide barometric pressure readings from the MAF sensor, so I cannot confirm its accuracy. Another common suggestion points to a vacuum leak in the PCV valve system as a potential cause. My main question: Why is Bank 1 showing a lean condition while Bank 2 remains unaffected? P.S. I recently replaced the fuel filter with no improvement. Any expert insights or troubleshooting steps before I proceed with component replacements? Thanks, Wes