SX pump cavitating
 

I have installed a brand new SX pump and it's making a very weird noise (like bubbles in the line or difficulties pulling). I have a filter right before the pump. and a -10 line about 12" long to a sump tank. Anyone sees what's wrong here? The pump was replaced thinking it was defective but the new still doeas the same thing. I also flow tested the pump with a bucket of gas and flows fine without making the loud noise. Any ideas?

Thanks,

Angel