Desert...
I would not call it that. I think it's more like Walbro ignorance, which is a curable condition [X(]

Midrange burbling (running rich midranfe) is cured by decreasing the idle needle (and if need be richening the H-needle), until the burbling stops, and the engine runs down nicely, and will spin up nicely. Settings will change with running in, so a re-adjustment now and then is in order, until these needle things settle. It takes some feeling for the engine what is just right, and what is too lean. Too rich does not hurt much, too lean means deadsticks.