Is riffing a word?
lol, at what happened to this thread!
Called pumper carbs because they pump gas from tank. That is why tank can be mounted below center line of carb.
Other than that, fuel/air mix enters engine no differently than a bowl carb.
Obviously, a diaphragm carb can be mounted in any position, whereas a bowl carb cannot.
Not all diaphragm carbs are pumpers.