If you have not, while you have the lower plastic off this is a great time to check carb synch since new plugs and accurate idle speed are good starting points. Once set it will probably stay that way for a long time. I am going on 3 years since my last carb synch. When checked last it was still spot on. Any drop in power delivery or mpg might indicate a check is on order, then it is done for a long time probably.