Can anyone tell me what's going on here? With some of my cartos (seems random) I occasionally get this whistling noise on the inhale (like a little mini Darth Vader, drives me crazy). In other words, the draw seems very 'airy'. With others, it's fine, a nice tight draw & no sound effects. Using a Volt & SI cartos. Fresh battery, not low on juice in the carto. What's up?