misfire between idle and higher rpm

82 Xj650.......bike starts and idles fine. When rpm's get higher it sputters until it reaches a certain rpm. Then, it revs up like it always has. No tach, so I'm not sure of the specific rpm in which it smooths out. This started a day after I washed it. The bike is old and I bought new coils(wires) and end caps. No difference. Removed tci box and desoldered circuit board. Nothing (looks) abnormal on circuit board. As bike warms up......the #2 cylinder exhaust pipe is the last one to get warm. At a higher steady rpm. The #2 cyl pops/misfires on occasion. Went through carbs and cleaned them. I don't believe it's carb related. Remember, this started happening the day after I washed it. The tci box controls the ignition advance on each coil right? If so, each coil fires two plugs. Why is it that it's only one plug misfiring? Any suggestions on what to start looking for?