Power loss

[Planger]

I have a e99 f250 that about 3 years ago swapped to a gtp38r turbo. I have 4in turbo back, afe stage 2 intake, and a banks big hoss stage 4 chip. I am only making about 22lbs of boost. My bottom end has gone away, and my millage has gone to about 12. I am thinking y pipe leak? any ideas? also I am looking for some more power. What do you guys think, I tow a 10k trailer. Thanks.

[Planger]

So I took it to the shop that put my exhaust on, and they said I had no exhaust leaks. none from the manifolds, or the ypipes. I'm stumped I am only getting about 12 miles to the gallon.