https://www.youtube.com/watch?v=KsZ4BCfMoFY is how it would sound. see how much deeper the sound is compared to your high pitched tone?

OR if you want you can put the 4.8iS exhaust on and then remove the center resonator and install an X pipe in its place to get this sound...
https://www.youtube.com/watch?v=IMwDHDLu34w

so you removed the 4.4i mufflers/boxes, STILL have the center muffler/silencer/resonator then installed straight pipes and welded on oval tips?

if you're looking for a slightly more racetrack sound, thne I'd recommend installing a sealed air intake system, like the Dinan air intake box. I just did and the sound level agian just went more beautiful but ONLY when you drive it, not when it sits and idles...

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I swear, my cars are like a girlfriend.
Sometimes its a rough ride, sometimes its smooth motorin'.
Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
BUT at the end of the day, she loves it when I am inside her.

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'91 850i
'05 X5 4.4i
'09 Clubman S