Kensington AUX cable for iPhone, Noise Reduction

Have in my BMW, the iPhone 4S is connected with a normal quality AUX cable and had extreme background noise such as noise, overlays, the volume had to turn up the volume to anything at all to hear the music, and then, as I said with extreme noise. Have tried, even with another iPhone 4 and BMW, but always the same number of AUX cable. With my predecessor iPhone 3GS, however, I had this problem not. (Same car radio itself)
Have the cause of BMW landfilled already, the work on it.
By chance I found the Kensington AUX cable. Ordered, unpacked, plugged in, WORKS !! Super price / performance.