Probably not much help but I have noticed that problem sometimes with my 7.3. Mine seems to be cold related as in if I run in to the store or something and let it run in sub zero temps, when I come back out I have zero boost and that wooshing sound. I am assuming that my waste gate is freezing open. this problem resolves itself within a mile and back to normal. I plan on starting with replacing the waste gate. Hope this helps you.