feedback w/ CS-3 problem

Hey, I have a Boss Compression/sustainer with a line 6 spyder II 2x12 amp. With it at high volume I get quite a bit of feedback, and i think it is the sustainer. I was just wondering if there was anything I could do/get to fix this problem. I can turn the level down on the pedal, but that reduces the overall volume alot and I still sometimes get feedback, even when I am far from the amp.

Any help would be great.
Thanks
ktm293