1996 ford f250 pulling P0171, P0174 codes,. Checked for vacuum leaks via carb cleaner, no leaks changed vacuum hoses, 02 sensors, fuel pressure regulator, pcv valve, maf sensor, egr, still pulling the same codes still. Any ideas?

Tim

 

I would start by measuring fuel pressure at the rail. Both key on engine off, and running, then test it under load (during acceleration).