No one has mentioned the HID lights ballast. The Xenon lights are High Intensity Discharge lights which require a high voltage, which is created by a ballast. Modern day ballasts are electronic (sometimes also referred to as digital) and can operate at frequencies in the 10s of kilohertz range. From the research I've done it looks like most vehicle HID ballasts operate in the 450hz range, which is more along the lines of bass than a high pitched sound, however, if the ballast does in fact operate at a higher frequency and there's a grounding issue the noise could possible show up in a variety of places. The most likely would be speakers.
While the fuel pump is a likely problem, I'm not sure it would create a resonance frequency of around 20khz, the frequency where human hearing cutoffs and appears to be the sound that people are hearing.
If the ECU is also operating at a frequency in the same range it could also create the problem if there's a grounding problem, it's just that ECU's operate at a low voltage and I would think it's too small to create the issue at hand.
This is all speculation and guesses, but figured I'd throw it out there.
|