Took the car for a drive today and could tell that the exhaust note wasn't as loud compared to last time I drove it. I have a American Thunder muffler. Also, when I rev, it starts popping. Never did this until now. When I start to get on it there is little to no drone. I used to have a bit of drone and now there is nothing. I don't understand how the exhaust note can change all of a sudden. Has anyone else experienced this? Any thoughts on how to fix it?