A CSI works alot more like a n2o solenoid, because they're nothing mroe than solenoids. Don't run a CSI through an injector driver. Run them through a pwm solenoid controller - like for varriable n2o.
And CSI's are really only good for tiny overhead. Most are only 75-125cc worth of fuel. (15-25bhp N/A max)
If you just want to use one (I have on several Toyota v6's). Hook them up to a $15 boost pressure switch.
Or in your case, if you buy an SMT6 to run your second fuel pump. Say, turn the pump on @ -2 through 0in/hg of vacuum in the manifold (Atmospheric pressure). Have it turn the CSI on at that time also.