Since I never had a + before, I was playing around with the air-control thingamabob. I noticed that it started to faintly whistle the more open it was. It could just be air whistling over the controller screw that's causing it. I don't intend leaving it that open anyway, so not too concerned about it.
Just FYI, the air screw is pretty responsive, I found just a quarter turn would make a perceptible difference.
