That engine in a motor home was known for eating up spark plug wires due to a lack of air flow across the wires and manifolds. I would make sure they're performing like they should. If they they're the OEM wires, I would replace with a good quality high temp set, along with new spark plugs.
It's always recommended that you take the coach out and get it good and hot (freeway running) before you test. They'll test cleaner when hot.
I don't know about Canadian smog tests, but my neighbor has been having a hard time getting his 2008 Ford V-10 to pass. The smog tech was entering it as a 10K GVW. My neighbor argued that it was a 20K chassis, but the tech said it didn't matter. He finally took it to another shop and they tested it as a 20K chassis and it passed.
