On the E53 I love the Dinan single walled tips. On other vehicles I prefer dual walled. I think the factory ovals look goofy. I really like Happy's exhaust because it reminds me of my e90 335 and hints at a boosted 6 under the hood.

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Again Daily Driven SC'd 4.6iS, whats the point of having a sweet ride if you dont use it all the time.