Switch try opening up the low end needle 1/2-1 turn and see if that won't help get the engine to idle . Then adjust the High Speed needle from there, then go back after the HSN is set and redo the low end. Also the vent plate mod is a very good one in my book, all of my engine's get it weather they need it or not just in case. Oh do make sure the screen is clean, if that gets partially plugged up it can cause idle problems plus other issue's.