Hi, I just bought an 07 GT and when the weather got cold a week or so later, I noticed the rattle untill it warmed up. I called the dealer and took it in. Just as my description was as close as yours, the mechanic guessed it was the sep plate so I took it in and they confirmed and had to order the part so it goes back in on Monday. I still have until Aug of 2013 on the warranty since I purchased a certified vehicle so it wont cost a dime. A couple of questions though, what do you think of these other guys sticking foam in there? Is it just because they have no warranty? Also, I just purchased a k&n cai and am wondering if it will void my warranty? Of course, I'll keep my original parts just in case. You had a great post, ( I just typed in the part# that was on the sheet that ford dealer gave me and it took me right to this forum and when I read your post, it was exactly the same thing I stated to ford(symptoms). I feel better now after reading your post, that kind of told me that the dealer mechanic knew of the problem. Thanks again