Get a vacuum gauge snchronizer. It is basically four glass tubes with mercury in them which are connected to each of your carbs with clear flexible hose. Motion Pro makes a nice one for about 40 or 50 bucks. It´s easier to do if you can take off your fuel tank and rig up a temporary fuel supply. The idea is to adjust the throttle linkages so that each carb is doing its share of the work and they´re not fighting each other. Once all four glass tubes on the gauge show the same vacuum level, the carbs are in synch. It´s not very difficult if you are familiar with mechanical work. I did my ZX-10 about 3 yrs ago. It wasn´t running poorly, but my brother bought the mercury gauges and I figured why not. Mine runs great, always has.