Lean under load

You have a century ahead technology air/fuel measuring device on a century behind air/fuel mixer. You will never get a carburetor to be 14.7 at idle, 14.7 part throttle and 14.7 at WOT. Ain't gonna happen. I agree about the step up spring. I think you can get it closer than it is, but it will never be perfect, simply because it's a carburetor.