I'm willing to bet since the OP has aluminum heads they should be a closed-chamber design and the compression should be at least 9:1...? In that case the burn rates are higher than with factory open-chamber heads and low compression meaning the engine will tolerate leaner mixtures than it would have stock. Just pointing that out for some peace of mind, everyone's scared of running lean but until you hit stumbling and misfiring it's really not hurting anything. I don't like the idea of running rich in any case except heavy load or WOT because you're just wasting fuel that's washing down your cylinders and actually wearing out your engine faster than needed.
