Whats the trick for getting stubborn album art

In most cases, Synergy can and does find the alubum art. Sometimes it does not, but I can certainly fid it on amazon.com. Whats the trick for altering my id tags to get it to find it.

When I revert the tags back, will synergy still use the cached album art?

I really dont want to add the art to iTunes, I just dont have the drive space to do so.