@CT
Just note, there are at least three situations here, although for us to know that IC might require people to post up. Sounds like there is something at the front of the car where Al is, something in a car near Flicker that may be what Luz/Ghost heard, and the RV situation (plus the ghouls which I am not counting yet).
EW Question: You may use EW in place of Perception if using a Sensor Array. Based on the wording of the book, it doesn't seem like it's required and, if only using a single sensor, doesn't appear to be allowed at all. Personally, I always use EW for arrays rather than allowing both, but that's just me.