air/fuel ratio

its been a while since i have been on here... but i wanted to know if anyone knows how to adjust the air to fuel ratio? please help my truck idles real high like ridiculous high

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well ill try this but im not sure its this cuz if i take off a vacuum line thats under the air filter housing almost next to quarted moon pieces ur talkin about it goes back to normal. but if i attach it, it takes a while to start increasing the acceleration

ok does anyone know what goes in this half moon? (in the red box)
it looks like some wire goes there cuz theres like a holding place in the back (the yellow box)


and this is what i used to disconnect to make the engine go from extremely high idle to regular
what is it?