things that should be checked....fuel pressure, FICM voltage(input and output), ICP pressure when cranking(needs 500 psi to start)....
what year truck? maintanance has been kept up(fuel filters, oil changes)?
have you tried different tunes? tried going back to stock prgramming?
only other thing i can think of, is an ICP (sensor or wiring)problem, but that should set somekind of code....