Because the 7 series are so quiet, too quiet, no engine noise and no exhaust it never feels like you are driving fast. So what I wanted to do is to add some better sound to it and install an exhaust, after some research I decided to go with magnaflow muffler, part # 14445. The cost is little over $70 dollars for this muffler. Install will depend on your local muffler shops. I was quoted $50 to weld this one on and they ended up charging me $40 since the install took only about 25 minutes.
Picture of the muffler is what the muffler looks like. There are 2 mufflers under the car, side by side, smaller one and a larger one. This magnaflow muffler replaces the smaller one. There is also a butterfly vavle that is stock and is on the smaller muffler, I had it cut off and transferred onto this new magnaflow muffler so it doesnt stay open at all times, only when you rev the RPMs past 3000. However there is a way to keep the valve open at all times for you exhaust to sound mean all the time. I will take some photos and show you guys.