Have a hayward super II on my filter. Also a ozonator that connects to a check valve on pump front. I was getting a lot of air so I found that the check valve was bad. I replaced it with a plug for now but I am still getting a little air. On the suction side about the only thing I have left to check is the valve in front of the pump that switches between pool or spa drain. It's a jandy neverlube with a jva 2440 on top. My pool supply store says these are notorious for letting air in. I don't see any water coming off of it and the only way it could be letting air into the pump is through the shaft on the valve itself right? So maybe try replacing the valve o-rings?