Gen 1 calls for 44 PSI. !!! I run 34 psi unloaded on Nittro Ridge Grapplers.If you run 38/38 like the door placard says, you’ll get great economy, have shít traction and wear the center of the KO2’s at 2x the rate of the edges.
I started dropping PSI after Raptor Assault a little at a time and keep it around 34-35 F, 33-32 rear with cargo and rotate frequently.
Good luck.
Ford can't officially recommend a tire pressure less than what it takes to handle a fully loaded truck on the hottest day at highway speeds.