If your using the stock wiring loom (i know i would) then just chop the wires at the ecu side of the loom, and splice in the -ve coil wire to the microtech. the +ve coil will already be wired to a 12V Voltage Source.
The E is just an earth, isn't really required.
If you want more information on this, have a look up at the Bosch coil conversion that some people have done to there skylines, they leave the Earth wire disconnected when using Bosch HEC716 coils, as these only have +ve and -ve connection points.
Or better yet, if you don't want to wire up anything, microtech have plug and play adapters for most of the RB's. Just gotta ask.