You can try this from another thread posted by LemansX5 to reset the throttle response. Might be worth a try?!
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Originally Posted by LeMansX5 View Post

Reset throttle response:

1) Insert the key & push the start button. (Don't touch the brake pedal & don't remove the key at any time)

2) Press & hold the accelerator down for 10 seconds.

3) Without releasing the accelerator push the start button.

4) Release the accelerator.

5) Wait a full 2 minutes.

6) Start the car normally & drive to see if it's more responsive.

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2007 328i Sport, Monaco Blue
2011 X35D - sold -Space Grey
2004 X5 4.4i - sold - Kalahari Beige
2001 X5 3.0i - sold - Pearl Beige
2006 325i Sport, Sonora Beige
2000 323i - sold - Sienna Red