Tach signal problems probably require a resistor on one of the wires in order to get proper voltage to go to whatever has the highest demand but maybe not. Most of the problems I have heard though have been backwards, where the ECU gets too much voltage and the tachometer lags behind or doesnt even work because the ECU is hogging all the voltage.
I have my car apart sort of and I am having a friend add a jumper on my MSII board so i can run direct coil (sohc = distributor
).
Going to grab an extra engine bay wiring harness and then just cut out all the extra wires and make a harness that I can tap my MSII signals into for relays and tach output etc.
Are you 3/S dohc guys running Ford EDIS or do you have a way to use the stock ignition setup? From Keithmacs post it sounds like "not yet."
To run a sohc motor, all you need to do is run the the distributor ground wire to the megasquirt, wire up batch fire injectors, and hook up the relays/sensor. Super easy!!! if you are familiar with the wiring.