I have the same set-up in my 02 F250. I don't think I've ever had the problem you're having though. I think you said you have the Big Hoss module is that correct? I know I don't have that so there may be a difference. I know in my truck, the only time I've seen 25lbs of boost is hauling ass towing the boat (7000lbs) up the 5 (grapevine). Otherwise the boost is not supposed to be that high and neither is the exhaust temp especially if you're not towing. Again, maybe the Big Hoss module allows this. As far as the power falling off, I would say that it would have to be a turbo problem and possibly the wastegate keeps getting stuck open..? I think your best bet would be to call banks and I bet they could tell you what's wrong. Good luck and keep us posted.
-Tom