My '07 A8L does not have Sirius and am taking it to be installed next week, I looked in the trunk area on left rear where Nav. is and can not find any wire loose.

Am I looking in the correct area or did they mount the unit somewhere else on these?

 

That is the correct location.

There is a retrofit kit that has all the correct cables to jack it into the power and MOST ring. No idea what the part # is.