Been trying to clear and fix error code p0301

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"Have a 1997 Honda accord LX 4 cyl. Been trying to clear p0301. Replaced spark plugs, wires, dist, rotor, pcv, and cleaned the egr. When the car is cold, start up and idle fine until it warms up. Then it idles a little rough. drives fine until you stop at a light, then I have to keep the rpm up a little. Could it be the TPC sensor? please help