I also fought a "chirping noise" for a long time. I think it was one of the 2 issues.
1) I noticed after rejetting that the stock hose clamps on the intakes were bottoming out before really locking the intakes in place. I feel I had a small intake leak. Replaced them with the SS ones from Brent.
2) Also noticed alot of chirping (sounds like a cricket)when I had the 45 mains in, mostly in the 1/4 throttle range. It went away after going back to the 42s, and getting the A/F ratio correct. Chirping... could it be the sound of the cylinders being cooled by too rich of a mixture?
All my chirping seems to be at bay now.
