S/C'ers and MPG

I have a saleen series II. rest of my mods are in my sig, and I get about 21mpg on the highway. 15 around town. The eaton is only supposed to draw about one third of a horsepower when not under boost because of the way the bypass is setup, but mine did go down when I installed it.
 
about 18mpg with 380+rwhp in an automatic convertable with the top down. 50/50 city highway driving. the car is running very rich tho. i need to tune it in.

i'm running 10psi from a Vortech.