you can get the harness from any greddy dealer or from greddy directly
Greddy web link to to electronics and turbo timer harness... they sell for 10.90
if the install is like the 1G (assuming you have a 2G) the hook up is under the drivers side dash... remove the dash panels under the dash and follow the ignition switch wires toward the firewall, find the plug for the ignition switch... it was the only plug that looked like the "T" part of the harness.... unplug the ignitin switch plug and "T" into it with the harness... put your dash back together and you are good to go
I didn't know what I was doing when I did mine and it only took like an hour to do