Hey Medicman, Marvel Mystery Oil may get rid of sticky lifters, but if its clicking its probably just the injectors. No big deal. Mine started doing that a few months ago, but eventually ceased. I think it was shortly after I did an oil change, and put in some of that Duralube engine conditioner. That stuff worked pretty good. Quieted the engine down nicely. But, the box says its not an additive, it's a "conditioner". Whatever the heck that means....
But I'm not sure whether oil, and engine conditioner could affect the injectors. Maybe it was something else. How long was it since you changed the oil? Mine took a few days to subside after the oil change. That is, if the oil change did anything to stop the sound or not.