Does anyone have access to an electical manual for the IS so we can determine exactly what the gray wire is and what other wire(s) might work?
I have my sub amp hooked up with the gray wire as the amp turn-on (based on your original post). My system seems to work fine. What symptoms did you have that made you think this wire isn't good? Maybe my amp uses the turn on differently than yours. Neither one should be drawing much current at all. I've played my system at 12:00 for an hour straight without problems.
Spectra Blue Mica/Ivory
LS, LD, HH, SR, 17" wheels
2000 Jeep Grand Cherokee Limited
4.7L, QuadraDrive, UpCountry
Patriot Blue, Fully loaded