I just got my new Avic-Z2 installed, and whenever the headlights are on there is annoying humming/buzzing coming from the speakers. It is not engine noise, b/c it doesn't get louder when I accelerate. I took my car back to the place that installed it, and they said they made the level of the noise decrease, but it still sounds like crap. I don't like driving at night, b/c of this. Does anyone know what I can do to fix this (Besides play my music loud)? Thanks...

Poor grounding issue? Sounds like you are getting a ground loop. If so, check your grounds and make sure they are "good"...in that they connect to bare metal...not painted. If this is ok, consider a ground loop isolator if you running after market amplifiers.