I bought 2 megaflow kits for my tank. It was obnoxiously loud. I ended using the adjustable pipe and remaking the top into a durso. Probably could have been fixed by adjusting the return flow a bit. But the durso top worked to silence it.
I also noticed in the 90 degree pipe on the return there was a little pin hole that was letting air bubbles into the loc-line and filling my tank with bubbles.
Zal that pin hole is to break the siphon if you lose power and the tank drains to the lowest part of the loc line or to the pin hole dont block it