I had the same complaint, it went on for a while. I replaced all the plugs, EGR, and only CHECKED the coil packs. One coil pack was a little funny so I replaced it as well, it's hit or miss with the stupid coil packs but the problem was there some times and kept coming back. My mechanic kept telling me to change more coil packs, but holly crap $$$$$. I ended up with a misfire code on #3 and #8 (with my cheap OBDII from Canadian Tire), I changed those packs and it runs like a dream now.
Hope my pain helps you.