The Input Level switch (on the back) is on Guitar and the instrument input setting is on Guitar as well (as opposed to Bass or Synth or whatever the other options are). Same thing with the second PF I tried.
I'm playing single notes, and none of them are outside of the key. There are no effects in front of, or after, the PF (except for my amp's reverb, which should have no effect).
I'll try adding a little delay and see if that helps.