Blue smoke is usually oil, not fuel. Fuel is black, sooty looking smoke. The facts that it's only one pipe and that it get's heavier when you let off (high vacuum) leads me to think either an intake gasket leak (internal), valve seals, or rings in a particular cylinder. A look at the plugs from that side should tell you which hole it is. Do the compression test, if that one hole is low it's rings. If the compression test is fine or that one hole is a little higher - it's seals or possibly an intake leak. I don;t think it's the carb in either case. You've got something wrong in the engine itself.