I've ran stock cylinders with the same mods at around 310-320 mains with stock carbs. If you have porting I would think you would be a richer on your jetting. Where are you at? Elevation, temperature, compression, type of gas? Is it detonating? What are you running for a head? Is it getting hot? Did you run the jetting up until it started puking on itself then back down until it cleaned up? Then check your plugs. That's the only way I know to make sure you are rich enough and not smoke it. Do you have a plate in the airbox for the K+N? How is it mounted? Not sucking dirt or something?