The changer with FM modulator antenna pass-through module should mute antenna input when tuned to the specified station, so once the CD changer is connected, you won't get any outside noise on that station used for CD music.
I'm having the same problem. I get constant static, and the volume ranges from song to song. I had CarToys install it which did a very nice and clean job. Is there anything I can do to elimiate the Static in the background? The Freq Mod is set to 88.5. The only other Freq available is 88.9.