Look at post #22 in this thread. I did some tests on the difference between running servo motor at 12v & 5v.
There is also a PDF attached showing a concept to drive the servo motor with the 5v output, but stepping it up to 12v via relays. Don't know that this has been tried. I think that there might be a small issue where there could be a hysteresis (chatter) affect. The Ignitech Vboost output (open percentage of VBoost butterflies) is different from the stock vboost output. Ignitech can be ramped up & down over ten user defined RPM points. To my knowledge, the stock VBoost is either full on or full off. The potential issue that I could see with the relay driven circuit is that if bike were held at a fairly consistent, but varying, maybe a 100 rpm, in the range where the VBoost was set to open, the circuitry may try to open and close (slightly) the VBoost to hold the opening that was set in the curve. There is a setting on the Servo tab that used to be called Hysteresis, but was changed when the V88 unit came out, still there, but now it has 2 input fields. I have not worked with it though.
Gary