Just an odd thought here... what if it's an especially microphonic capacitor? All caps are microphonic to a greater or lessor degree, condenser mics are just capacitors that are designed to be microphonic. What if Cusack got a bad batch? You could try tapping each of the caps with a stick with the pedal hooked up to an amp. If you find a suspect cap, a little dab of hot glue should help to secure it to an adjacent component and can be removed pretty easily.