On my '89 single cab GMC truck, the muffler was a little louder than the original manufacturer's. My engine has around 400 hp. It was just too quiet and I felt like it was held back a bit at high rpm. Years ago I had a 50 Series Flowmaster in my little Toyota V8 4.7 and I remember its annoying hum in the four door cab, especially at 60 mph. With an additional 150 horsepower in this truck and a two-door cab, I wanted a rumble at idle, but I didn't want any OBVIOUS cab hum on the freeway. So Iβ¦