Its ALL in the tune my friend...
We have a (somewhat) similiar setup, and I'm putting out over 380 at the wheels (@8lbs boost too...), although your torque numbers (@ 370) compared to your RWHP on a blown setup are actually pretty good....
Are you still running the stock MAF?...
(I don't know how you could be... What size injectors?)
I highly recommend a custom programmed Pro-M MAF for your application... it should free up some horsepower, and depending on your injector size, may help with your fuel curve...
The Anderson Power pipe should help a bit... here is a link:
http://www.andersonfordmotorsport.co...es_frames.html
Considering how the tune is SO important...
It might be worth the money and the drive to go somewhere to get a custom dyno-tune done.....
I have found that a custom dyno-tuned AutoLogic chip seems to be the way to go, although I have seen no real issues with the Diablos either...