Pump Lags when returning water to pool.

I thought it was my pool filter causing this strange noise, It sounds like the pump isn't fully primed but it is putting out a good amount of water to pool. I cleaned my DE filter this morning, but it didn't help. I played with the valves a bit to try and figure out what is causing this noise. It only happens when the valve is allowing water to return, to the pool. When the valve allows water to return only to spa the noise goes away. I am thinking something is could be stuck in the pipes going to the pool. You know when you adjust the valve for the pool vac and the skimmer, and you have to much suction on the pool vac side.... thats what it sounds like. There is a decent amount of water returning to the pool but not as much as it used to be. I know nothing could of gotten stuck in the lines because it would have to come out of the pool filter, then through the chlorinator grids.

I pretty much ran out of trouble shooting to figure out what is wrong, but anyone else' ideas would be greatly appreciated.

Thanks.
Mike

Well I thought I would ad an update:

I have 4 Northstar 2HP pumps and I swapped out the main filter pump with a water fall pump and the noise went away. So I figured it was the pump's motor that is getting worn out. It was good for a day and a half, Then this morning the Starving pump noise returned.

Well I think it's Fixed now. I had some crap in the props of the pump, and I also lubbed the heck out of all the seals. Pump works like a champ again.