With this solution you can fast open low z injectors and fast close(30V flyback) but with 30% pwm(low energy losses on flyback transistor).
When pwm last, flyback voltage is 0.3-1.5V(depending of schottky diode and mosfet(irf9540))
Bad thing is, you must have one of thise flyback for every injector.
PCB
Assembled board(missing 2 zener diodes, i bought two too few)
That board was tested on lpg injectors(landi renzo, 0.9ohm) and working well.