Another issue that's a little more serious that n case that is worn throttle shafts. When thy get sloppy enough, the throttle plate can sag down (or whichever way the sping pulls it) and hit the side of the cab throat, leaving it propped open a little. This gradually gets worse as the wear gets wose, and eventually the throttle plate even starts carving a notch in the carb body that makes it harder to un-hang.

You can check for throttle shaft wear easily, just wiggle them by hand and see how much slop there is.
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'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)