The original video sounds far to loud for a DD, and the fact that it's an auto convertible really would mean the exhaust just doesn't make sense. A car in that trim doesn't need to sound like that, and your resale value would plummet as the target consumer for that vehicle wants a comfortable sporty convertible (sorry to sound mean but a Chick who just wants to look good is far more likely than a performance enthusiast). I think if you Did the "custom made" catback idea from a local muffler shop, and you had it made with flanges instead of a welded system. Then when the auto finally bores you to the point of wanting to sell it, you could switch back to stock. Then sell the custom exhaust separate on the bimmer forums.