Hi all. I'm not too good with engines so please forgive me. I just replaced my John Cooper Works cold air intake filter and accidentally pulled out the vacuum tube without noticing it and drove it for a day and a half quite hard. I Realized something was wrong and put the vacuum to back on. Now my engine hesitates when shifting in the low gears as soon as I hit the throttle for about half a second then power resumes. I have a 2005 mini Cooper S John Cooper Works.
Thanks

 

Follow the vacuum line down to the bypass valve and see if you also pulled the line from the bypass valve off.

If you are sure there are no vacuum leaks, reset the adaptations, as the car will learn around having vacuum leaks.

 

I should mention that this does not happen on every shift.