2007 1.6L, P0420 and P0303 DTCs and 'Clack-chirp' noise from motor idling in park.

[kestrel]

2007 Chevy Aveo 1.6L, 193K miles.

I have had a recurring Check engine light with DTC reader giving P0420 and P0303-Cyl 3 Misfire codes.Video demonstrates knock-chirp sound from engine while in park at idle. Have not been driving since noise developed. I did replace throttle body due to uneven-bucking acceleration that produced above codes. Ran better for a while with no CEL or codes, then problem returned. About 28K miles ago I had a full top end motor rebuild at reputable private shop with all valves / springs and some lifters replaced, head machined, new timing belt, etc. after timing belt broke and bent valves.
Any opinions on what this noise is?
https://youtu.be/D_TWINuUf6M