My 104 surged too, I have a 96 so it was not the wiring harness but a vacuum leak from a bad Purge valve that was not closing. After that was replaced the car ran like new. If it isn't the cat it is likely something air related (MAF, vacuum leak, etc..) or your harness. Your harness connects all the electronic devices to the computer and the computer controls the idle, when there is a bad signal the computer will increase the idle to compensate for what it things is increased air flow. Good luck!
Brian

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Brian W. Heitman

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