There is no measurable benefit from a cold air box from a standing start because the maximum amount of air the engine can use is not limited by the intake system volume capability Adding a Dinan air box and then using intake tubing, MAF, or throttle body that is smaller in diameter decreases the benefit of the air box even with a matching tune.

IMO order of priority based on best ROI is low restriction exhaust, transmission software, air box and all matched pieces, and then matching tune. The only well researched and tested tunes based on many thousands of lines of code considered and lots of dyno and real world testing that is currently available for an X5 are from Dinan.

Unfortunately, it is necessary to do many dyno runs to establish a baseline and more to verify the improvement. Even then ambient temp and humidity will vary results. Timed runs will get you in the ball park but there are lots more variables and you can only see where improved or loss of performance was in the dyno HP/TQ curves. Because the X5 is so heavy and with 4 wheel drive it won't break loose even with the addition of 100 more on the torque side, I have focused on the best possible TQ curve rather than best possible HP ramp.

While throwing some rain on this parade, new and lower cost performance improvement ideas usually come from DIYers. And it is possible that the complete Dinan system is overkill. They are always conservative.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas