Ahh, I remember when my S sounded like a beast too. But I fixed it. You should too.
The reason being is that there are a multitude of wires running above the exhaust under the carpet inside the car. Holes in the exhaust can direct hot exhaust up at the floor and create hotspots that melt the plastic insulation leading to shorts and many many nightmares trying to figure out what exactly the problem is. Or it can melt spots on the carpet or catch things on fire.