You need access to the amplifier that is behind the rear seat - I only had to fold the rear passenger seat forward to gain access and remove the seat back cover to get to the connections. It's a tight fit, so getting the connectors loose was a little bit of struggle for my large hands. That said, the Nicestuff harness connects at two of the connectors towards the middle of the amplifier. A connector at the far end of the amplifier, closest to the driver's side of the car (US centric) is the same shape, as one of these two, but it's not the one that needs to be connected.
I should have snapped some photos, but didn't get a chance.
The harness makes the installation plug and play - except for the ignition connection - that I grabbed from the power lead to the 12V power socket by the shifter on the center console.
I think one of my earlier posts ( http://us.lexusownersclub.com/forums/index...st&p=312664 ) details connections on an earlier RX amplifier.
Hope this helps...