My 302, ( which most are military versions) is exactly the same. I don’t see the benefit of restricting the exhaust in the full closed (#3) position as pictured above. My unit is also in the “closed” position. In testing my motor for idle/fuel mixture, it is running very rich. If that flapper is opened, I’m sure the motor will breathe better and lean out for the better? Why have better breathing exhaust if it is restricted at the collector? I think heat will be the only way to remove the nut and back out the set screw to reposition the flapper position.
