[MiniHomesteader]

If holding the choke helps…presumably closed some. That means it is running lean(ie not enough fuel). Air filter will probably help, but either adjust the main jet open a little bit. Also you said the carb is new. Is it a Briggs carb or a chinesium carb? One last question, when opening up the throttle, are you sliding it up, or cracking it wide open?

 

[MiniHomesteader]

My guess is that that carb doesn’t have a main adjustment, just the idle. Most new carbs are set lean to begin with. Can you post some pictures of the carb?