In a book I read years ago - might have been Gen Doolittle's autobiography - was it "I'll Never be so Lucky Again"?
He mentioned that mods had been done to the carburetors of the engines to allow maximum range and once the aircraft arrived in California a person returned the Carbs to "Factory settings".
This was only discovered after the ships were at sea and settings could not be returned to the special settings.
My memory is vague as to the details.