I have examined and tested nearly a dozen different carbs for .60 and larger engines. The only carb that I have found that is almost perfectly tunable at any range, and on any engine from .60-1.8 cu.in. was the old OS 7M-7H. No two adjustment carburetor can be tuned to work best over a multitude of engines and exhaust combinations, many are designed specific to its engine and application. Adding a pump changes everything and will nullify a lot of your previous tuning knowlege. Its not easy but all issues and mysteries can be solved with enough time, effort, and selection of carburetors.