don't have the dyno graph, but I will try to explain as clear as possible.
a little history first. car was last dynoed on march, 2004. car set up is B18C1 83mm with full-race manifold and T4 pt67 turbo. car made 597 whp @ 26psi at around 8k. had to let off due to falling fuel pressure. re-did the fuel system and tuned over. ran the car ever since without redynoing. last week decided to dyno the car as performance was weak. where I use to trap 124-126 on 17psi, now only trapping 112-115. something didn't seem right. dynoed the car @ 17psi and made 410whp@7k , power dropping off to around 325 till 9000rpm. turned the boost up to 26psi and made 526 whp and 371ft lb. again the power was falling off after 7k. does this seem as though the turbo is failing?

 

maybe your turbo is goin bad make sure you got no whole in your charge pipes or the couple's i know my car all the tq on the pipes seemed to rip the couple apart

check compression and leak down