SportTruck

Hey guys, I have an 2003, which after warmup looses a very noticable amount of power. It will run great every time it cools down util it reaches operating temps. Am showing code 251, injection pump fuel metering control. Changed metering sensor, no help. It is a timing or fuel pressure issue somehow because my adjustable ts performance box (timing and pressure) has no effect on power once warm up occurs. Also my tst box will blow alot more smoke(like retarded timing ) with less power once the truck has warmed up. I have tried removing all boxes and or swaping boxes, same effect. HELP!