Can anyone help with a k&n induction kit on a vrs tdi

Hi everyone, I've recently joined the site as ive purchased a 2011 VRS Tdi, I'm loving the car but I recently bought a k&n induction kit, I'm not completely useless so I've fitted it myself following the instructions step by step, I'm not sure what I was expecting but the car now sounds like a compressed air leak!! it builds up at the start of the revs then dies higher in the revs, then reoccurs when you come off the pedal and let the revs drop, I'm not convinced it's meant to sound the way it does but can anyone advise if they've had similar issues or if I've maybes missed something? Thanks in advance.

Si.