No accounting for shade tree actions.... RTV is never a good thing to use around fuel and fuel vapor unless it is a specific formula. He may have tried to use old gaskets that had already been imprinted with another carbs pattern. That is a common cause of vacuum leaks and is often how base plate ears get broken off of carbs when guys try to cinch it down to stop the leak. You can reuse the gaskets sometimes if they are indexed correctly and off the same carb and spacer setup only!