Shep, I think you have your gain up too far, and its simply feedback unless there is something very wrong in your wiring. Remember the Evo have some fearsome output, and that much gain, well there must be microphonic stuff happening. I use a Boss MT-2 with my Legacy for boosting gain. With the Legacy on about gain 6, I have to put the MT-2 on only about 8 o'clock, barely any distortion on the dial. Much higher and my Freds start to carry on as well. Try dropping your gain, and really listen to the tone, I think you will have plenty of gain, sustain and tone from your setup.