hey, i have a set of dynomax super turbo mufflers on my 85 gt mustang, and they sound really good at low rpm,s in 3rd at 60kmh, and in 4th at 80kmh, the sound vibrates through the car, but the problem is when i go a little faster like 4th gear at 95kmh the sound totally goes away, all you can hear is the engine, is this the way most exaust on peoples car is or no. i want the sound to be there all the time. or would better mufflers give me that sound all the time.