Suggestions for muscle car sound muffler without drone

I am sold on this technique. I finally got a free morning with my bro in law and we put the pipes on. The drone is gone, period. I honestly can't believe it. I'll post photos later today. There is still a beautiful muscle car rumble from the exhaust out back but no drone. I drove up my test hill which I have to always drive on the eay home and we can talk, listen to the stereo. You hear the pure exhaust rumble and that's it. My ears have been saved.