This is one of the most fantastic plugins I've seen. Allen, thank you for making it available. I may be missing something but I cannot get the plugin to suppress the source or many things at all. It simply ignores the parameters. In addition, there is no spacing between the source and the actual excerpt, at least not in my version. So you'll get something that looks like this:
My Blog - The Greatest EverWe could talk about my blog for a long time and you wouldn't even know it existed....
So in short, everything works very well except for the ability to suppress the blog/feed name:
[wp_rss_multi_importer category="2" showgroup="0"]