Well, you need to trace the wire from the actual VTEC solenoid (for example) back to where it plugs into the harness going into the car. The VTEC wire goes to one of the connectors on the passenger side right at the strut tower. Use a continuity tester to make sure you have the right wire. When you're sure, you can either cut the wire or just splice into it and then run it to the ECU yourself.

Check out this tutorial: http://www.c-speedracing.com/howto/b18cswap/swap4.php

Their wiring is a little vague and it really messed me up so don't read that part, but you can see how they ran the wiring.