That vent has only one purpose, and it has nothing whatsoever to do with how the engine runs. it's there to provide a way for vapors to escape from the float chamber during hot idle to prevent the engine from loading up at stoplights. Normally, the vapors would be vented into the air horn through that big angled port under the air cleaner. Go ahead and tinker with it, as it's also connected to the accelerator pump linkage, but you're spitting into the wind concerning the problem you're chasing. Ask Grace Slick what happens when you start going down rabbit holes!
Jerry
