Well I noticed a small rattling noise a couple days ago under normal acceleration. It will quit when I get on it hard and it only does it in drive under light load. If you put it neutral and rev it up it doesn't do it. I made a video of the noise i put drive and held the brakes while giving it gas and put it in park and revved to demonstrate. http://youtu.be/u4GpSlfzzk0 could it be spark knock?