wiring diagram for R34:
http://www.installdr.com/Harnesses/Nissan-Wiring.pdf
it is the 2nd diagram, should be blue going from what it says
there is one in the standard loom
if you tested all the wires with a testlight and couldn't find an ignition switch, check that your radio fuse hasn't blown
if it hasnt blown and you still cant find the right ignition wire, make sure your testlight is grounded right