Credit goes to the Miata.net guide (link below) that gave me most of info. Images below just help to make things alittle clearer.
http://www.miata.net/garage/flash.html
(General housekeeping - This mod is to the best of my knowledge safe, but please perform at your own risk!)
The Diode i used was purchased from JayCar electronics. I simply asked for a 3amp Diode at 1kv. Cost me 30cents!

This first pic shows the ignition barrel and steering column. Access to this is made possible by removing the steering column cover. 4 screws.
The plug in question can be seen above the ignition barrel in white.

Pic of the disconnected plug where the diode will be placed to perform the short.

Diode inserted. Locate Red/White and Black/White wires and insert the Diode as shown
NOTE: The stripped side of the diode must be on the side the feeds into the Black/White wire <---------------------

Ive used electrical tape to ensure the diode stays in place.

Plug reinstalled.

Be sure to test before reassembling the steering cover.
Enjoy!