How did you check the coil packs?
I had misfires on my 03 a while ago and couldn't find the cause. I ended up replacing all the coil packs and haven't had a problem since.
If you haven't run any seafoam in a while, that can help clean things out.
Could be one of the coil packs isn't fully seated? The one on the passenger side that has the bracket on it would be the first one I'd look at. Make sure the bracket is really seated properly, not just 'kinda' seated properly.
When did you last change the plugs?