Lean mixture could only happen if the carb could pass proportionally more air than fuel. I suspect that the lack of an accelerator pump may come into play. Emissions were never mentioned, but he was trimmed to run stoich at 14.5:1. He does mention that it is well down on power, but apparently it maintains enough power to run 80mph - just takes a while to get there.haven't watched this vid, but how us he getting that kind of mileage without running it super lean, and creating NOx as a result?