I apologize in advance if this is the wrong place to ask this question, but does anyone here know about how Howell triggers their TBI systems that don't use the ECU for timing control? I know on the GM TBI ignition modules, there are 4 wires that go to the ecu (EST, Reference, Bypass, and Ref Low). Just curious if anyone knows which one is the main signal input wire. Also, am I correct in assuming the GM ECU relies on a 12v squarewave pulse to fire the injectors? If so, could I run an optical distributor such as a Mallory Unilite dizzy?