The Main problem you will have is the flat squashed part of the super charger piping if you can have that enlarged some way i think you could make more than 300hp with a pulley change.
I know its been a while but I was wondering if you had access to the fuel map that you use. At the mo Im going with the 7 injector set-up driven by an SMT6 and I could do with a starting point. Wounldn't the extra injector have to put 1/7th of the fuel that goes to your 6 injectors?