Did you have a AIT sensor after the interooler?Yes they SAY 1 hp for every CC, however, in reality that isn't always necessarily true. Lots of other factors to consider.
I had a very similar setup and was maxing out the 550's at about 450rwhp, which if you calculate 15% drivetrain loss, you are looking at 515-520hp at the crank. So it was very close to that.
In order to break the 500rwhp mark, I had to jump up to 680's and a Greddy 3 row. The Cartech/Spearco could cook eggs on it after a couple dyno runs at that power level.