The fuel injector idea is cool, it has its own solinoid system and can be PWM'ed to vary the flow, however, higher end M/W systems already have PWM control, Coolingmist does.
Problem with automotive EFI stuff is generally there psi range is 70psi or less. Not sure if auto injectors would like a 100% duty cycle. Need to weld bungs in for them and a hold down fixture since there just oring ended. Electromotive has those holders. Newer stuff may be more but not likly near 250. Not sure if the existing M/W pumps would like having a pressurized inlet feed. They may be internally regulated for a 250 max output? And iirc they are a diaphram pump, again pressurized inlet pressures may adversly affect that?