I am by no means an engine expert, but my dad taught me a trick years ago when I was trying to keep a 1946 Willys Jeep in operating condition. If you suspect the throttle shaft area is excessively worn, shoot carb-cleaner on the throttle body while the engine is idling. If the engine speeds up, you've got a leak problem. Note that this is NOT as simple to do on an aircraft engine.... Ron Wanttaja