I'm getting a lot of air bubbling in one of my return lines. I recently upgraded my pump motor to a EVQ 225 VS motor. When I run the motor full speed, I don't have any air in the system. When I lower the RPMs below 2750, it pulls air in the system. I've checked for leaks multiple times using the incense method. I've verified all of the mounting bolt are snugged to the suggested torque settings. I added Magic Lube II to the pump basket lid. It still leaks. Could there be something other than a suction side leak causing the issue? Also, the bubbling only happens in one of the four return lines. I've attached a video where you can see the difference between the speeds. Let me know if you have any insights. Thanks