Im not sure which cells you are referring to, but it sounds like BLM's are what you are asking about. I dont know that you would necessarily find an exaust leak making drastic blm changes. Something like a vaccum leak or otherwise would cause a problem with the blm's, but not an exhaust leak. I cant think of any way you could pinpoint an exhaust leak with DS, except with maybe slow spoolup or something odd like that. Perhaps someone else can, though.
Bob