you can pick up a total kit for about 4 grand, at 7 psi, not to bad, they are pushing, 394 hp and 449 tq at the wheels...then you can get the upgrade wich requires more tuning, (not sure of the price) and get up to 12 or 15 psi.
12 psi creates close to 600 hp and over 630 lbs tq...at the whells...supposedly...sounds like a great set up to me, i'll be getting one shortly...(hopefully)... here is the link to their site..
www.ststurbo.com