If it is the MSD, and you're using the big capacitor noise filter they recommend, and you have the big power and ground wires installed just like they recommend, then the only other thing I can think of would be that the spark plug wires are not spiral or helically wound wires, which they gotta be, or that they're cracked and crappy. Solid core wires on an MSD unit will easily produce electrical noise -- helically wound wires won't. Other than some sort of goofy bad connection/ground type of thing, I can't think of why the MSD would be doing that.
