Yeah I know I could increase the flow going down the emergency but the problem with that is then it makes the loud gurgle. I just tried lowering the emergency and still nothing doesn't the same thing. It's really starting to get to me! It has to be the cornerflow design doesn't it? Whenever the vortech is off it stays adjusted fine but then when I turn it on bam suddenly the herbie won't keep up.It could. There are things you can do to quiet it. I secured some filter floss just under the inside of my overflow to reduce the flow noise. Over time it will develop a build up that will quiet things down, also.
Just thinking about it, and I missed the obvious. You could increase the amount that trickles into the emergency drain instead of lowering it. This would be the easy answer. Set your MP40 to max flow, adjust your valve, and when your MP40 slows down it should increase the flow through the emergency drain without dropping level.