Like I mentioned on my previous rants, '03 X5 4.6is will not have any sound difference whether you remove the resonator or not. I don't know why BMW installed it in the first place. I replaced the resonator with a Magnaflow X-pipe and it still sounded the same. There was no full throttle sound that I expected. As Weasel mentioned before, 4.6is has different timing with the 4.4, 3.0, and the 4.8's. Maybe because it is built to beat up on those ML AMG's! I'm looking into straight piping the two mufflers though. Let's see what happens...

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2003 BMW X5 4.6is
Black on black with black wheels,
Black grille, Smoked tails, X-pipe