I have the same problem...(2000 7.3L 4x4), except not quite as bad as yours. A couple of quick questions. Does the interference "chk" change speed with enginer RPM? Mine doesn't. Also, is it there without the engine running, but with the key in the 'run' positions? I only have the noise when the radio station signal strength is weak.

Mine isn't to the objectionable point yet, so I haven't traced it down yet. In my case, I suspect the fuel pressure pump starting and stopping.

BTW, I'm a 55 year Ham radio operator and a Professional Engineer.

I don't have time to research the problem for about the next week - my wife & I are leaving for our summer snowbird trip (out of the desert heat). As soon as we get there, I'll see if I can trace my noise down. This is when I do mosts of the mods to my truck. PM me so that I can have your return address.

Bob