Trying to Help a Ford friend w/ problems.

[CRSmith]

A friend of mine has a problem with his powerstroke. Like everyone here, I'm a dodge guy, so I don't know any of the little quirks that could cause this on the fords. Anyway, sometimes when he mashes the go pedal, the truck bogs down and smokes much like it has a clogged air filter, or restricted exhaust, or the turbo is lagging excessively. The truck will bog a few seconds and then start to take off. I guess the boost just seems to build excessively slow. He has some kind of power programmer, a straight-pipe exhaust, and that's about it. He's tried the air filter and that's not it. Is this a common problem with an easy solution that has been addressed with the fords before? Maybe some sensor that goes bad?
Thanks.