Hi, I have an A3 2007 and a couple of months ago I had a pioneer nav unit installed and I've had constant problems with radio reception. FM is Ok for the most part but tends to get interference from time to time but AM is really poor. There is constant buzzing/interference sound. Does anyone know what could be causing this and how I can fix? Could this also affect GPS/phone receptions as I get dropouts/inaccuracies somes of time.