I had the muffler & tail pipe replaced when I lived in CA from a well-known auto parts/repair shop when the car had 165,000 miles. Now I'm going to school in Maine and the car has almost 203,000 miles. I was recently informed by a mechanic that I need an entire exhaust system, almost $400-500. The car has a rough sound all the time, sort of like a motorcycle. Can it be possible that I need a new exhaust system?