My classic car has a new Chevy 350 engine and I had a new dual exhaust system with 2 resonators and 2 mufflers. He has a stock Chevy 350 with no racing or performance parts; has exhaust manifolds, no manifolds. I wanted a smooth, quiet ride. Unfortunately, the exhaust noise was terrible. I've visited several muffler stores and they had no idea what to do with it. After looking at the solutions, I replaced my existing resonators with these resonators. I also added 2 catalytic converters because I thought they could help without hurting me and I would drive cleaner. Almost no drone! There is still a little, but no more worries. I am very happy with the improvement and consider the problem solved. It would be nice to remove 100% of the drone, but I'm running out of ideas.