I use this made by me.
With this i can control the selenoids separately and the rpm scale goes from 500 to 8000 with increments of 500 to 500, I can share the pcb and part list if you like.
Set this via RS232 (serial) with a free software.
Originally designed to activate an additional injection system based on rpm and vaccum/boost but adding a relay and a capacitor can be used as multi switch
All pieces are in newark in one and the cost is around 40 dlls.