Well, I've run into a snag with my tune.
I got it dyno'ed and it put down 388 rwhp loaded (413 no load) at 8 lbs boost.
But the AFR was at 12.3, which is entirely too lean.
The low boost was achieved by putting a Steeda underdrive pulley instead of the one that came with the Roush kit.
So in the next month or so, I'm upgrading the fuel pump to the GT500 dual pump system and putting the stock lower pulley back on, which *should* generate 12 lbs of boost... according to JDM Engineering.
With the upgraded fuel pump and 12 lbs boost, and a better tune, I'm expecting around 440-450 rwhp with load. We will see. The car performs very well as it is, but there's more to be had. I'm not willing to got higher than 450 rwhp on a stock motor. One day I'll get a Ford Racing short block and bump up to 550+!
As for cost, I don't have a real number for the blower alone. I spent $10,600 out the door for the blower, Shelby GT500 frontend and hood conversion, painted mirrors, Silver Racing louvers, and some other smaller details (touch up paint on the car, extra 7-rib belt and some various labor cost).
Maybe a little on the pricey side, but I'm not complaining. I love my new car!