Ford 6.4 Power Stroke

Could be several things. Either going to be low fuel pressure, restricted exhaust, low boost

Could be several things, yeah — low fuel pressure, restricted exhaust, or low boost are all solid starting points for a bog with no power on a 6.4.

To narrow it down, pull codes first (even if the light isn't on), then check fuel pressure at idle and under load. If pressure drops off when you step on it, look at the fuel filters, HPFP, or supply side. If fuel's solid, check for exhaust restriction — back pressure test or pull the downpipe and retest. Boost leak or turbo issue would show up as low manifold pressure under throttle.

What year is the truck, and have you seen any codes or done any logging yet?