A dyno run will tell you the power and torque your engine is producing. Many (but not all) dynomometers also have an exhaust gas analyser that will tell you what your mixture is. With that, you can make an informed guess as to which way you need to go and how far with your jets, but you will find that it's going to take a few trys to get it exact. When you get the mixture closer to ideal, the engine will run better and that will change the air flow, and that will change the mixture so there is little chance of getting it exact on the first try, but you will probably not need more than 3 sizes to get it right.
