Pipe cleaners are great for cleaning out the air tube.
Also, did you remove the air tube and flavor wicks to dry burn? You really need to see the coil to dry burn. I find the flavor wicks generally aren't reuseable, and replace with a strand of cotton yarn, good fit, wicks well. Trim after putting the air tube back on. Sometimes the Davide (and other bottom coil units) will leak and gurgle if the flavor wicks aren't placed right. If using two strands of 1 mm silica wick they need to be parallel, not crossed. Sometimes the simple act of washing can skew them.
Also, did you remove the air tube and flavor wicks to dry burn? You really need to see the coil to dry burn. I find the flavor wicks generally aren't reuseable, and replace with a strand of cotton yarn, good fit, wicks well. Trim after putting the air tube back on. Sometimes the Davide (and other bottom coil units) will leak and gurgle if the flavor wicks aren't placed right. If using two strands of 1 mm silica wick they need to be parallel, not crossed. Sometimes the simple act of washing can skew them.