I was drivng my friends 328is today and when i would accelerate hard it would produce a soft but def audible clicking sound, like the sound of a playing card against the spokes of a bike wheel as it was spining...it seems to be coming from the drivers side rear but i could be dead wrong on the location... do u think it could be octane pings from a bad batch of gas? ive driven this car countless times and have never heard this noise before and my friend also denies any known problems.