Give it more servo travel.
Study your linkage for problems.
Have you taken the carb off to see how it works?
Does the carb have travel stops limiting the throttles travel?
If you have looked at the carb when off you could see where the throttle butterfly could close all the way. The head of the retaining screw should be pointing to you when closed. You might want to set up servo travel to be able to close the throttle all the way and give you a second way to kill the engine. And somewhere in between should be it's lowest idle. set your servo up so that idle is about middle of trim setting.

A massive intake leak will make it idle fast but your servo travel should be able to go past that.
Is there a gasket between the carb and reed block?