I have the same, heard it when I drove with the music off so I could listen to the car ( I do this every now and again) It only happens some of the time and from what I have gathered its nothing major so I just live with it.
Haha Abbas thats exactly how i noticed mine, just cant get enough of the engine sound. ;)
engine does sound so sweet!. had this on astra took a magnex to take my mind off it. i noticed a sqeek when i 1st got mine as well but only just remembered reading this post!! has anyone noticed the engine sounds even better with the aircon switched on? kinda growlier- i only have oem tailpipes