This might be the cause, check it out.

Yesturday I got in my truck, started it up and a horrible noise/rattle came from what sounded like from my exsuast(sounded like I had a hole in my muffler). Well, I ran around the corner to were I had my PV put on thinking a weld broke. After inspection the bolt from underneath the ECU valve(I think that's the name of it, #2 on the pic below)




holding the exsaust line coming from the what looks like the header came off, dropped down and was rattling like a pissed off diamond back. It was to hot to stick a hand in there to start the tread going to tighten it back up.
This morning I got it on with my hands and brought it over to my shop for them to put it on correctly with a little lock tight so it does'nt vibrate off again(not to much, because it's alumium(sp) and might sease the treads..they told me that).
After they fixed it, I noticed more pep and I bet that might be the problem for your boost loss, leaking exsaust, check it and see if it's loose.