You may have a couple separate issues going on. For the rattle, there was a TSB for the idler pulley where the bearings would wear and you'd hear a scraping/rattling sound. I had this on my SVT, and I also thought it was chain related. Take off the drive belt and start the car; if the rattle goes away its one of the pulleys, with the idler being the probable cause. Its a cheap part and an easy fix. For the misfire, when's the last time the plugs were changed?
I could be way off here, but I though I'd offer it in the hopes that you don't have something serious.
