Low basket suction

Hi, all. Just joined the forum. I've got a 20k inground with a DE filter running at 9psi. The Polaris runs ok (evidenced by it spraying water all over the windows from its tail), but my suction at the basket is really low. It's not even enough to suck a few dead beetles (not John or George) into the basket. After reading some threads about the main pump's impeller possibly being clogged, I tried backwashing it for about 10 seconds. The backwash pressure coming out of the MPV was impressive, although I cannot quantize it since I had no gauge on the output pipe...but it created a nice puddle in my yard after just a few seconds. Putting the MPV in recirculate didn't help the suction, which eliminates the DE filter (right?). So why is my basket suction so low? If the pump had an inlet clog, wouldn't that mean the backwash flow would also be low?

Sorry for the long post.