From your description, it sounds like a worn throttle body. You won't really know if it is the shaft or the bushing until you remove it and take it apart.
When the TB wears, it passes more air into the intake, almost like opening the throttle slightly, and the engine idle speed increases. As recommended, reduce the idle air by screwing the BBS screws in.
Until you rebuild the TBs, you'll have difficulty achieving proper idle RPM.
More photos please...