Hi,
I've just finished installing a Pure 300Di into my 2007 Lexus GS430 and thought I'd share, as various places said it was impossible when really, its quite easy!
I didn't take photos along the way, so this isn't a how to. There where a couple of things I was trying to achieve with this:
1) Ipod and aux input, with either on screen control, or a separate screen. CD Changer type playlist control wasn't good enough.
2) Decent sound quality, so no FM modulation
3) No cutting of factory wiring
4) DAB (least important)
This led me to use a Pure 300Di to give me a screen to control the ipod, as well as DAB and a GROM Audio Aux input to get the sound from the 300Di into the ML headunit. Note that despite what GROM told me, you do not loose the standard DVD changer by using the unit, when you press disc it goes to the DVD changer first, then if you press it again it goes to the GROM.
Not cutting the factory wiring was achieved by piggybacking the Pure 300Di's power off the GROM unit. In a nutshell the GROM plugs into the back of the nav unit, then I tapped into the GROMs ground, 12V battery and 12V switched wires for the 300Di, meaning that if I remove the GROM, the 300Di is removed as well.
The wire colours for me GROM unit where: Black - ground
Red - 12V battery
Yellow - 12V switched
BUT please check yourself with a multimeter, there is no reason why another GROM unit couldn't have a different layout!
I'll report back once I've done some more miles with the setup, but for now I'm happy!