Fuel pressure loss after engine warms up

[DarrenKling]

Truck has normal fuel pressure at idle and down the highway until the engine is at operating temp... Lift pump pressure stays the same as fuel pressure starts to drop,I retorqued the fuel injector lines to spec already, for example with scanner hooked up to truck down the road setpoint is 17k it matches actual but as engine works up down the road setpoint is 17k actual is between 2200-7k where do I start?