Old car guy stuff. (Both old guy and old car)

Just because that weird fuel thingy on the top of your engine has brass screws with flat-head screw driver slots, doesn't mean you should tighten them as much as possible.

In the image is a new "idle mixture screw" (center) smoothly machined, conical tip to allow a predictable about of fuel through a small hole when the throttle is closed.

On either side of the new screw, are the ones originally removed.