You migt want to try using some really thin wire(the thinnest you can get) to make up some upside down J to put in the idle bleeds, all eight That should inrichen the mixture all the way through the entire RPM range If that fixes the miss you know your on the edge of a lean misfire at part throttle operations. The next move is to get a set of the next smaller I.D. idle air bleeds, maybe.001 to .003 smaller to fix it Make sure there are no vacaume leaks also