more detail...vacuum gauge reading is rock solid, no wiggle in the needle, at any steady throttle setting. With engine off and choke disengaged, secondary throttle plates open fully. I presume air valve opens with vacuum, as I have to manually operate it with engine off. There appears to be a little discoloration around accelerator pump plunger. There is no fuel odor or liquid fuel other than inside the bores. Carb throat and plates are immaculately clean.