If I did this mod this is how I would wire it up.
I would essentially use a relay harness like many people use with any form of HIDs. I would run the Bi-xenon "activation" wires off of the high-beam relay. I would also run the factory Hi-Beams off of the Hi-beam relay but I would put an additional toggle switch between it so that you could turn off the factory high beams and run only he bi-xenon highs.
I made a quick-n-dirty wiring diagram. Hopefully you understand what I'm saying a little better.
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I realized that i forgot to put in the diode that would be required between the high and low beam relays. You'd need a diode between the signal terminals of the high and low beam relays so that the low beam relay stays active when the high beams are engaged.
Hopefully that wasn't too confusing. I didn't want to spend a whole lot of time on it.