I bought and installed a vance hines muffler and stage one jet kit. The Kawasaki dealership installed the jet kit. The bike runs great but pops once in a while when I accelerate. I have noticed its much more responsive in lower gears but seems to have lost some on the top end. What can I do to improve the top end? I have looked into the 385 upgrade but its costs prohibitive at this point. I drive on the highway alot and would like to use a 16tooth sprocket for lower RPM's and gas mileage.