I tend to leave my low end rich and have the high end set so it holds rpm in full throttle vertical uplines. I like mine to burble a little when doing 3d - If your flying imac you can run it leaner. I had one quit from being too lean and broke my plane up awhile back. Ever since then I've left it rich. You have ot be careful doing alot of 3-d as it'll lean out when it gets hotter and hotter. I have mine rich enough that it burbles the whole time just a little. If it ever stops burbling when you're doing 3d you have to let it cool off a bit.