If you can, I would recommend getting access to the wiring diagram for the 4runner first.
I've only had mine for about 4 months now, but still not brave enough to do any kind of hacking and wacking on it.
Anyway, it is unfortunate that the low beams do not turn off when you turn on the high beams on the current 4runners (my '99 Olds Alero does this...low beam off when high beam on...damn DRLs...). Because you could have put a relay inbetween the + and - wires of the low beam that turns on and allows power to flow to your aux lights...when the low beam turns off, the aux lights turn off.
I think what you are going to need is a 'reverse' relay...a relay that is by default 'on' and you apply power to it to turn it off.
So, when the high beams are off, the above relay will allow power to the aux lights...then when high beams are turned on, the relay 'disconnects' power to the aux lights.
As the saying goes, there is more than one way to skin a cat...sorry to the cat owners out there...;-)
There may be more that one way to do this...this is just off the top of my head...
I would try to tap into the wires going into the headlights themselves...if the headlights (along with everything else) is controlled by a BCM (Body Control Module...like my Olds), then it is simpler to hack into wires at the end.
Why the need for the wire diagram...well, in older cars I've worked on...the headlight bulb was always grouned, and to turn it on, power (via relay and switch) from a 12V source was provided. No so anymore...I discovered on my Olds that the BCM actually controlled the lights and that headlights were, what I called 'reversed' wired. This means that headlight bulb was always connected to a 12V source...when I turn on the headlight switch, a signal was sent to the BCM which in turn applied ground to bulb, thereby turning it on. Strange, huh?
So, you'll have to know which wire (+ or -) is constantly connected and which one gets 'applied' when you turn it on or off...in order to wire up the relay properly.
