Mano, thank you for reply! I'm not sure I understand very well. I think the module should match sobi2 meta keywords to joomla content meta keywords plus look for at least x matches. Such functionality would be more than enough for me (I don't think I need matching of other sobi parameters). Module FJ Related Article Plus does that well for articles but obviously doesn't work with sobi. May be some of the code from this module would help you. Unfortunately I don't know enough about php programming to do it myself.
Thank you for any help.