1994 Lexus ES 400

1994 Lexus ES 400 Front Wheel Drive Automatic 214855 miles

While on my way back from a 5 mile drive yesterday my car experienced a problem accelerating and idling. The gas pedal is boggy and " puttery". In my Honda it was the spark plug wires, when I had similar symptoms. I have pulled each plug wire to check them and don't feel that they are bad. The engine changed idle when each one was pulled. It is making a deep, loud hum, almost, out of the exhaust. The RPM's are going about 1000 higher than usual before shifting What else should I be looking for?
While the car has a lot of miles on it (214855), it was purchased from an older gentleman and was purchased by him from a dealer ship as a previously leased car. It has been properly maintained by the dealership regularly.
October 21, 2010.

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