Interesting. So you are going to taller gears redliner? Wondering how different that would feel... factory is the 3.91's if I am reading the above correctly? I'm sure you are unconcerned with MPG... these tanks aren't great on that anyway. Some extra jump off the line could be very compelling. Interested for sure.

Did this on my auto Mustang GT (travesty, I know, it was purchased before I could drive manual)... and it made a huge difference.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
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