It didn't happen for me. I ran 2 1/2" pipes with Turbo mufflers and turndowns in front of the rear axle back in my 350 chevelle days, I used an H-pipe. In the couple of years I drove the car like that I didn't notice any fumes and the sound was just right, no drone. That car made several long trips, like 500 miles, so we would have noticed.
