Well you really need to sort out if it is either rich or lean............If you are not running the air corrector set up, you might be able to ride it to the point of missfire/ stutter and perhaps mute the bellmouth with your left hand to see if this makes it better or worse, not block off the air all together, just a couple of fingers across to restrict the air flow. My Eso/Norton was not coming back on the power cleanly out of the corners, this with a 36 mm Mk 2 concentric on methanol, the slide was a number 3 from memory, way too rich. I modified the slide to a number 5 and now the engine is as clean as possible out of corners now.