I put a k&n panel filter into my standard airbox approx 1 month ago. The car was due to go in for a service today so last night i put the standard air filter back in to make sure any numpties wouldnt replace my k&n for a standard one [just in case]. I was out in the car last night and i can honestly say the car runs far better with the standard filter.
With the k&n filter i was noticing some hesitation on acceleration and pick up that is completely gone with the standard filter. It is totally and noticably different to drive.
Any explanations why the car doesnt work as well with a 'performance filter'
Ps. the k&n filter was brand spanking new when i put it in.