LED & HID lights can cause a tremendous amount of RF Interference. One fix to improve this is to use a ferrite choke, sometimes referred to as RF choke. Both names are referring to the same device.
Ferrite beads help eliminate interference in two directions: from a source or to your radio. A conductive cable like the input power cord for the HID or LED headlight bulbs behaves like an antenna. The device that produces radiofrequency interference, this can be transmitted through the cable, which acts as an accidental antenna. In this example, the bead may be required to lessen RFI. If other items are generating RF interference, like an alternator or injection pump, the ferrite bead stops the cable from acting as an antenna and receiving interference from those other sources
Ferrite chokes are already utilized in everyday items like USB cables, GPS power cords, home surround sound systems, and many others.
Another option for an LED conversion kit ferrite coil which is more extensive and is designed for the power cable to be wrapped around it several times.
You might be wondering where can I buy them? There are many places, too many to list. Amazon does have a large selection to choose from, click here to be taken directly to the product page on their site.