Have a '97 Tiburon 2.0L with less than 50K actual miles that has an intermittent miss only at speeds above 50mph. Was driven only in small rural town for at least last 8 years. Now want to do some out-of-state traveling. Have changed spark plugs, plug wires, and fuel filter. Still has same problem. No engine warning lights. Fuel filter was partially blocked according to mechanic. Put fuel injector cleaner in fuel tank. About to pull-out what little hair is left. All help will be appreciated.