i have a 93 del sol,d16z6 motor,auto trans.normally it runs fine around town but if the weather is hot and i drive for an hour or so on the freeway when i pull off it starts missing and running poorly at stoplights.once it cools off its fine again.plugs,cap,and rotor have around 10,000 miles on them.i pulled the plugs and other than a little carbon they looked ok,so i cleaned and reinstalled them.any other ideas?