I have a 3.0i with the Supersprints and straight pipes. It sounds pretty awsome...but I was curious about what you mentioned losing power and the back pressure with the straight pipe. I'm not sure if I sure if I actually noticed anything, but sometimes I feel itmight not be pulling as hard, not really sure. I am considerng to switching to the X pipe.

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2010 BMW X5 ///M
Silverstone Metallic
Black/Black Merino with Black Piano Trim
Premium Sound
Driver Assistance
Comfort Access
High Gloss Roof Rails

Gone but not forgotten: Upgraded!
2003 BMW X5 3.0i
Titanium Silver
Navigation
Cold Weather Package
Premium Package
Heated Steering Wheel
20" wheels (275/45/R20 all around)
Supersprint Magnum Exhaust
AFE Cold Air Intake
Bimmian Chrome Guage Rings
What's A Resonator?