If it's just sniffer testing, no reason it won't pass if it's tuned right. Unless you are in CA, pretty unlikely others have gone through exactly what you are attempting to do. Since the rules vary state to state, it's hard to guess at what you will have to attempt. I mean here we have the emissions test done on a roller dyno, and diesels are smogged, I bet those alone are different than your test...
Visual inspection is another story...true duals in your case is a federal law violation, so unless they do a visual and don't care about that, you'd fail. You say sniffer, so I assume no underhood/undercarriage inspection. We don't have an underhood/undercarriage inspection here.
