After reviewing my post, it seems I could have explained why anyone would want to open up their wah and start fiddling around.

Basically, what happens when you move that little plastic piece (or rotate the potentiometer) is that you are now sweeping a different section of the wah's total range. E.g. your wah has a total frequency range of, say, 1-100. Pedalling from lowest to highest accesses a frequency range of, say, 35-65. Moving the plastic piece (or rotating the pot - can't remember exactly what's needed) allows you to move the pedal range from 35-65 to, for example, 65-95. Thus, you'll be wahing higher frequencies. Make sense?

Anyways, my intel may not be 100% up-to-date on how exactly to move the range since I now own a Dunlop 535Q that has a little knob that does this for me. It should be pretty obvious, though, once you open 'er up.

Let me know how it goes!