I don't know what you are running for a prop but a big heavy prop will help your idle such as an APC or Master Airscrew 13/6 or maybe a 13/7. You might want to use the fuel the carb was calabrated for at the factory with which is 20% oil and 15% nitro. This might help due limited adjustments of that carb. The OS F plug is the standard of the industry and because four strokes go through very few of them, I can't see much reason to use anything else.