i would lean towards an air leak.carb gasket or carb mount on pipe.
check the cap that screws on top as well.
if raising needle didnt help and lowering it didnt help,the next course of action would be choking it while driving to see if it worsens.then something i tried was to close the tank valve and drive it til it runs out of gas.mine smoothed out and started to pull,i opened valve a little to keep gas coming in,but its impossible to regulate it.
lowering float adjustment may also lean it out a minute amount,as it takes a little more to lift the fuel.
i bought a set of small number drills,and soldered the jet closed and redrilled it two sizes smaller.im at #76,think i could go smaller.