Ive heard alot of people complaining of valvetrain damage by over-reving there F20. Of course I heard of this AFTER quite a few sprints to redline. Heres the thing though, ever since I bought it ( USED) about 6 months ago, cutting the car off to go in a store or something then starting it back up while still hot results in a terrible rattling noise that I cant pin-point. All I know is that if I listen close, I here a click, then a " weee" sound like something is powering up, and it stops. Plus, I dont have the clicking noise when it is cold. I went back to the dealership and they said it is the heatshield on the header and that all they would do is take it off. So I wasn't gonna pay them to take it off. Any ideas what it could be???