I have had the occasional TQ 'whistle' at small throttle openings. These were carbs that had no shaft wear, so I do not believe it comes from the air leakage at the shaft. Only had it happen on modified engines that needed more idle air. I think, but have no proof, that the noise is a combination of the particular air speed, air volume & throttle opening that coincide to produce the whistle...like blowing across the top of a Coke bottle.
I can pull back on the linkage and make it stop and it will idle all day long without doing it until the throttle cable pulls the linkage forward again and it starts whistling. There is slop in the shaft allowing a good bit of movement
