My idle was acting kinda funky after miscellaneous engine bay work. I saw a thread recommending to change out the old, dry rotted vacuum hoses. It's only been a couple of days, but I haven't noticed an idle issue since. Some of my hoses were in pretty rough shape, so maybe one of them got disturbed just enough to throw things off?
If you want to give it a shot, it's 5/32" (or 4mm) and you'll need anywhere from 6' to 11', depending on whether you want to change out the three longer runs. I picked it up for ~$1/ft at Autozone.
I'm also wondering in your case if it could be something about the plugs/wires themselves. Did you use dialectric grease?