I have just puchased a 03 VY S2 Exec V6 Auto only 20000kms, have noticed an abnormal noise when slowing down from about 70-50 km/h. It is not always noticable.I could best describe as a faint knocking sound. One holden dealer told me they could not hear it and RAC noticed problem but could not determine cause. Any ideas or similar problems out there, so I have some info before I take it back to Holden???