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Here are some notes from a Wiki (generic):
High hydrocarbon emissions from a vehicle may be caused by improper ignition timing, faulty ignition, misfiring problems, vacuum leaks, worn piston rings or valves or an exhaust gas recirculation system incorrectly operating at idle. One fouled spark plug can result in extremely high hydrocarbon emissions. Start by replacing the spark plugs and plug wires. Replace every single vacuum line under the hood. Replace them one at a time, so as to not get confused. Clean you EGR Valve of any carbon deposits, and make sure it is functioning correctly. Pour a can of a good Fuel Injector cleaner such as Seafoam or Techron in a full tank of fuel. Leave the cheap stuff on the shelf, as is does very little good. To remove built up carbon deposits, inject it through the intake by following the directions on a can of Seafoam. Have someone check the timing on this vehicle. Check the smog pump to see if it is functioning. A compression check will verify if you have worn rings or a burnt valve.
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