I checked out both of the links from your first post. There is no such thing as a universal muffler so I would not purchase either of the two.

It is good advise to save your $$$ for other things but it is your decision what you want to do and when, so, if you are going to buy using Ebay at least find something that specifies it will fit your X5 with no or a minimum of modification and cost to install. Also, purchase from a seller that has a 98% or better satisfaction percentage from a great number transactions and 5 star vendor. If you do so, you will not know how it sounds, let alone exactly, but, it will be inexpensive. The other inexpensive option is the delete option where you have a better idea what it will sound like but still not exactly. Everything else in comparison to the these two will be expensive.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas