I also recommend the Eisenmann race mufflers......I have them on my 4.8 as well. Be warned though, the pics they show on the Eisenhaus website are for the 4.6. The mufflers look the same, EXCEPT the 4.8 mufflers do not come with any connecting pipes. You simply get the two mufflers, and they have about two inches of pipe sticking out the back that need to get welded up to your stock pipes.

Make sure you have a reputable shop do the swap. They will have to cut off your old mufflers and weld the new ones on. In my situation, the pipes were not lining up so they had to cut some of the stock pipe off and fabricate their own with custom bends etc... It was alot of work, but the sound is absolutely intoxicating and well worth the hassle. I get compliments all the time, its unreal.

Just wanted to give you a heads up! Good luck!

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2005 X5 4.8is
Sapphire Black / Black