How long were you running the car with the wires cross connected? Did you drive the car in this state for extended durations? You might be able to isolate the problem to a specific cylinder by pulling individual plug wires one at a time until you find which cylinder is making the noise.
Did you replace the plugs with one of proper heat range? Did you damage a plug? What is the condition of the plug wires if damaged or old they could be cross firing two cylinders.
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