Most are familiar with the process of "bushing" a throttle body to eliminate the slop between a throttle shaft and the bore which results in inconsistent idle speed issues as well as vacuum leaks. However, sometimes the shaft itself can be worn as well, and if that's the case, often it can not be repaired and needs to be replaced. This is an issue I run into quite frequently, and unfortunately there's no way to know if a throttle shaft is worn w/o removing it from the throttle body.
While some shafts will wear out on the ends, far more frequently on Holley carburetors I find them worn in between the throttle blades where there is only a small section of casting that supports the throttle shaft.
As you can see in the pic below, this particular shaft was worn both on the throttle operator end and in the middle.
Thankfully this is most often limited to earlier carbs that utilize a throttle shaft made of brass. The later carbs with steel shafts seldom exhibit this issue.
There is no practical way to build this worn area back up, and as such this shaft is destined for the scrap pile.