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Question: Knock sensor on 2000 Nissan Quest-

On my way home late at night, my tachometer started jumping a little, and the engine was rough. Then after another minute the lights dimmed and the engine died. It wouldn't start again. The next morning, it started right up, and it seemed fine. Drove it to the mechanic, he took it for a drive on the freeway, then after he got off the freeway it died again and had to be towed. The error code on the computer is P0326- Knock Sensor. I had the same sensor activated a couple of years ago, and my awesome mechanic (sadly, we have since moved far away, so I don't have access to the same guy) gave the engine a tune-up and replace the spark plugs and everything was fine (well, for two years). The car has been idling rough, and the intake manifold may be warped. Could the intake manifold cause this? Distributor? Any ideas?