Have you measured the noise higher ? Or just hear the noise higher ? For this kind of things only a proper measure will tell you if there is a problem or not.
As mentioned before if problem there is it's probably an impedance related issue.
Another consideration is that an electric guitar pickup is basically a coil, so with the volume pot it forms a LR low pass filter, the higher the parallel resistor (lower part of the pot) the lower the cut frequency and the more the high freq is attenuated. So it might just be that your pickup is picking up some high freq parrasitic signal that is just attenuated enough with the pot up but less and less when the pot goes lower. Some ballpark/back of the envelope calculation using your pickup's typical inductance (good pickup manufacturer do spec that) and the pot value might confirm if that can be part of the issue or not, this cut frequency might well be beyond audio spectrum, on you to check for that.
If the noise are high frequencies consider low passing instead of a wide band follower, guitar signal don't have much high freq even in audio sens of the term so that can't harm. Somewhere around 5kHz is probably a good place to start.
In a more general scope, lots of noise problem in audio electronics comes from the layout, not from the schematic, so you might check that as well if nothing else seams to work.
Just my 2cts...