Hi, I'm new here. I had my BMW for two years now. While my car was on a warranty, I brouht my car in for repair because I noticed that one of my mufflers was always spotless while the other was blackened with dust. They told me nothing was wrong and that one was used for the city and one was used for the highway. Now that I'm off warranty and my check engine light turned on, I came back in there. It turns out that the engine isn't getting enough air from the exhaust. So now they want ~$135 for the repair and I was wondering if any of you guys can tell me where to get another stock exhaust for cheap or tell me how to fix the current one? Thanks.