I changed the intake of the overflow to this:
I used a 'T' pvc fitting to allow more air in. This fixed the gurgling noise problem when i had the vortech on short pulse and making waves. It used to gurgle a lot when the pump was in this mode. I figured it needed an air escape while draining, and it seems to have worked. The intake part (i.e 'T' fitting or 90 elbow whichever you choose to use) does not need to be cemented onto the rest of the pvc overflow. It's easy to switch around and experiment with.