Unfortunately the packaging didn't include schematic installation instructions for the recommended configurations. It seems simple enough but without a schematic I can't be sure. Anyway, I hooked it up as advised in my 2003 Ford Windstar but it did not remedy the noise problem. Perhaps this is due because the short pigtail of the filter plugs into the head unit, still requiring using the same, long patch cables. Because those patch cables connect to the amp after the filter there may still be an opportunity for picking up noise in the patch cables. Using shielded cables did not help so perhaps the signal noise is occurring elsewhere.
Next I will use adapters to plug the filter in just before the input of the amp to see if that helps. Still, the small price makes it worth trying. I am not an electrical engineer but happily, as I get older my high pitch hearing is worsening and so the problem is not as apparent as it was at first.