Try tapping into the factory knock sensor wire at the ECU, like we do with the J&S unit. Be sure to use a shielded cable, to avoid introducing electrical interference.
Here's how we make the cable that's included in the kit:
We use 22 gauge, twisted pair, with foil shield and drain wire. There are lots of different part numbers and cable brands that will work, but we like Belden 9461, because it's easy to strip.
At the J&S end of the cable, we connect the black and the drain wires to the system ground pin, then we connect the white wire to the knock input pin on the unit.
At the other end of the cable, we cut off the black and the shield wires, as they are not used. The white wire is then spliced into the knock signal wire, near the ECU. Make sure that you don't cut into the factory shield, as this will short out the knock signal.
darioc: Did you do a temp install of the knocklite on a J&S equipped car? Might be ok if both cars have similar noise levels.