Truck losing air pressure while stopped can’t find leak

[Redland1]

(04-27-2021 )Rawze Wrote:  Some leaks will stop when the air system gets below 90-psi... Put air up all the way to 120 psi and shut engine off, then key-switch back to on position, jump out before it drops back down.

The only way it goes up to 120 is if I drive it above 55MPH.