The hell with the dealers. If it is the same tensioner as the 11-15, you can manually adjust. Pull it out and pull the plunger a click or two out. It's a one way plunger. I would say go one click at a time. If you can't install the tensioner back in, you've probably pulled it out too far. But, if the thing doesn't fully seat (1-2 mm gap), toss the bolts in and tighten them down. Did this on a bike, got rid of the noise.
It is NOT the same tensioner as the Gen 4. It can't be easily adjusted manually like the older style.