This is on my White 1855. It’s surging bad at slow throttle and quits at low idle. Choking it helps some. Fuel delivery is good new hoses, new filter, & fresh gas. I’m going to take the top of the carb off to do some cleaning and making sure everything is clear. My first question is what is this what looks like a vacuum port with nothing on it. It’s at the top left corner. I don’t see any hoses or any indication anything was ever attached to it because it’s dirty at the end. This is my first twin I have worked on so I might be back with more questions. Thanks