When I installed my MSD box into my 93 civic Si I ran a wire from under my distributor cap to the ignition control module, from there to the blaster coil, and from there to distributor cap to be sent to each individual spark plug. Where does that original wire that I ran from under the distributor cap to the ignition control module come from? I wanted to know what gave my MSD box a signal.

 

the wire you ran comes from the ignitor which gets its signal from the ecu.

 

You got the trigger wire for the ignition. Its the wire that would be connected to points. Its the switch for the coil. It says "now".