So many suggestions lol
I had a ball valve on the drain but found it needed to be wide open just to keep up with the pump throttled back and at that time the drain was barely an inch under waterfall gurgled so took out the ball valve then added the T thing to try to give the air a way to escape that didn't work either
I'm not able to get behind the tank or into the bottom of the Overflow box so not sure how I can add a second drain without draining the Overflow box ie a lot of trouble lol
After throttling back even more it only gurgles every ten minutes or so lol better than ever few like before but it still causes a lot of splash in the lid of my sump