Okay, I'm going to ask this question, knowing that BOTH have a major impact on the sound of the exhaust. However, which has a great impact on the 550i (F10), when it comes to sound deadening? The cats or the exhaust? To me, the obvious answer would be the exhaust. However, knowing that the F10 is so quiet and having seen the stock cats in this thread, I just thought it might be worth asking. I'm no car expert, so please don't flame me too hard
So, which of the following statements would be true?
1) High flow cats and stock exhaust would be louder.
2) Stock cats and an upgraded exhaust would be louder.