interesting reading...i think the most common diagnosis is 'rich in the midrange'...i agree...my 1.60fx used to load up and quit when i reduced throttle...by carefully adjusting the needles, 1/8 turn at a time, the problem disappeared...imho, the first thing is to realize that the poor midrange and throttle response from midrange is a rich condition...my gp ss starts on the first backflip, pulls like a horse, and taxi's back to the flight line every time...no pump, stock muffler, 17x10 apc, wildcat 15%nitro/18%syn...however, if you don't fly where i fly (sunny hawaii at sea level) your 1.60fx might not be as happy as mine...lol...ken