Sorry for the late reply I was at MACNA since Thursday.
Noise would mean at some point the skimmer was submerged too deeply and water was sucked into the airline. Raise the skimmer so the marked water line is 1/4- 1/2" above the actual waterline. The marked line is the maximum, not the optimum. Close the air screw all the way, then unplug the skimmer and plug it back in, slowly back the screw out, this will create a bit of a vacuum and suck most of the trapped water through. There will still be some water and some noise but it will diminish over the next week as the trapped water evaporates and gets pulled through. This trapped water is reducing airflow and performance. Alternatively, you can disassemble the skimmer and drain the airline, but this is more complicated, though the result is immediate.