I had the exact same problem after changing the timing belt, please see the whole thread on this topic here: Low noise after changing the timing belt. The noise only occurred in a certain rev range, same as in your case. I was worried about catastrophic engine failure.
I replaced a number of parts with no success.
To finally diagnose the problem, I removed the TB cover (and serpentine belt, etc.) and ran the engine for a short time using a mechanical stethoscope to check the timing components for noise. This led me to the sprocket as the likely source of the noise.
I ended up putting the old toothed pulley back in, which I eventually replaced with a brand new one at 117k (25k miles later after the TB change) just to be on the safe side. I never heard the chirping noise again.
