I recently acquired a 1997 Z3 1.9L with a 5-speed transmission. The car runs great, but I have noticed what can best be described as a sucking sound (possibly low pitch vibration) when I release the throttle and clutch to shift after running the tachometer up to near redline. Has anyone else noticed this sound? If so, what is the source of the sound and does it indicate a potential problem or it just the sound of dollars going out the exhaust pipe?