I have a 2000 Grand Prix GT. There is a noise that seems like it's coming from the back fire wall. It only happens when starting and stopping. I can also make it happen by putting it in drive, foot on the brake and gassing it. Had a similar noise a year ago and the dealer replaced both lower controle arms, I had to bring it back because they mucked woth the cv jont boots causing them to split. they replaced both cv joints. I just did the front brakes, no change and I checked some of the cradle boolts, all ok. Any ideas??? I'm baffled