Do they even make such an animal?
If I were going to keep track of how things are doing down there, I would go for the exhaust gas temp and try and avoid a melt down about to happen. Unfortunately, most 2 smokers on fan only deal with this after the melt down and rebuild of the engine. But seems like this would give you piece of mind as you run down the trail and see where the temp is at. If it creeps up there over time, it would tell you that it is time to re-do the carbs and boots and prevent the melt down before it happens.
Too lean, means a burnt down machine.