I've slowly ran the barrel adjuster on the rear derailleur from the point where it downshifts to where it upshifts. Right now it's dead bang center to the cog below it. I've also moved the in-line barrel adjuster quite a bit both ways while pedaling. I don't disagree that this is the problem, especially since the noise seems to be coming from the rear, but there doesn't seem to be a sweet spot.