I have a 2004 E55 and every time I accelerate a lil hard and let go it makes this sound like a blow out valve or sumthing. I'm wondering if ne1 ever had this kinda problem. I never took it to be checked out. My friend has a 05 E55 and his doesn't do that. Someone told me it could be my belt. The car has 23,000k mile's. Any ideas???

 

most of time is either belt tentioner or belt